Form990-PF

Department of the Treasury
Internal Revenue Service

Return of Private Foundation
or Section 4947(a)(1) Trust Treated as Private Foundation
Do not enter social security numbers on this form as it may be made public.
Go to www.irs.gov/Form990PF for instructions and the latest information.
OMB No. 1545-0047
2025
Open to Public Inspection
For calendar year 2025, or tax year beginning 01 - 01 2025, and ending 12 - 31, 20 25
Name of foundation
THE RIVER FOUNDATION
C/O WALTER & CELIA GILBERT TRUSTEES
Number and street (or P.O. box number if mail is not delivered to street address) 15 GRAY GARDENS WEST
  Room/suite
City or town
CAMBRIDGE
State or province
MA
Country  
ZIP or foreign postal code
021382311
A Employer identification number

04-3254488
B Telephone number (see instructions)

6178648778
C
G Check all that apply:

D 1. Foreign organizations, check here.............
2. Foreign organizations meeting the 85%
test, check here and attach computation ...
E
H Check type of organization:
F
I Fair market value of all assets at end
of year (from Part II, col. (c),
line 16)$1,566,971J Accounting method:
 
(Part I, column (d) must be on cash basis.)
Part I Analysis of Revenue and Expenses (The total of amounts in columns (b), (c), and (d) may not necessarily equal the amounts in column (a) (see instructions).) (a) Revenue and
expenses per
books 		(b) Net investment
income 		(c) Adjusted net
income 		(d) Disbursements
for charitable
purposes
(cash basis only)
Revenue 1 Contributions, gifts, grants, etc., received (attach schedule)  
2 Check .................
3 Interest on savings and temporary cash investments      
4 Dividends and interest from securities... 47,919 47,919  
5a Gross rents............      
b Net rental income or (loss)  
6a Net gain or (loss) from sale of assets not on line 10 233,271
b Gross sales price for all assets on line 6a 665,704
7 Capital gain net income (from Part IV, line 2)... 233,271
8 Net short-term capital gain.........  
9 Income modifications...........  
10a Gross sales less returns and allowances  
b Less: Cost of goods sold....  
c Gross profit or (loss) (attach schedule).....    
11 Other income (attach schedule).......      
12 Total. Add lines 1 through 11........ 281,190 281,190  
Operating and Administrative Expenses 13 Compensation of officers, directors, trustees, etc. 0 0   0
14 Other employee salaries and wages......        
15 Pension plans, employee benefits.......        
16a Legal fees (attach schedule).........        
b Accounting fees (attach schedule).......        
c Other professional fees (attach schedule).... Click to see attachment
List of Attached Documents:
// Content
14,059 14,059   0
17 Interest...............        
18 Taxes (attach schedule) (see instructions)... Click to see attachment
List of Attached Documents:
// Content
573 0   35
19 Depreciation (attach schedule) and depletion...      
20 Occupancy..............        
21 Travel, conferences, and meetings.......        
22 Printing and publications..........        
23 Other expenses (attach schedule).......        
24 Total operating and administrative expenses.
Add lines 13 through 23.......... 14,632 14,059   35
25 Contributions, gifts, grants paid....... 296,000 296,000
26 Total expenses and disbursements. Add lines 24 and 25 ................ 310,632 14,059   296,035
27 Subtract line 26 from line 12:
a Excess of revenue over expenses and disbursements -29,442
b Net investment income (if negative, enter -0-) 267,131
c Adjusted net income (if negative, enter -0-)...  
For Paperwork Reduction Act Notice, see instructions.
Cat. No. 11289X Form 990-PF (2025)
Form 990-PF (2025)
Page 2
Part II Balance Sheets Attached schedules and amounts in the description column
should be for end-of-year amounts only. (See instructions.) 		Beginning of year End of year
(a) Book Value (b) Book Value (c) Fair Market Value
Assets 1 Cash—non-interest-bearing............. 39,664 20,074 19,946
2 Savings and temporary cash investments.........      
3 Accounts receivable 3,163
Less: allowance for doubtful accounts     3,163 3,163
4 Pledges receivable  
Less: allowance for doubtful accounts        
5 Grants receivable.................      
6 Receivables due from officers, directors, trustees, and other
disqualified persons (attach schedule) (see instructions).....      
7 Other notes and loans receivable (attach schedule)  
Less: allowance for doubtful accounts        
8 Inventories for sale or use..............      
9 Prepaid expenses and deferred charges..........      
10a Investments—U.S. and state government obligations (attach schedule)      
b Investments—corporate stock (attach schedule)....... 1,374,781 Click to see attachment
List of Attached Documents:
// Content
1,361,766 		1,543,862
c Investments—corporate bonds (attach schedule).......      
11 Investments—land, buildings, and equipment: basis  
Less: accumulated depreciation (attach schedule)        
12 Investments—mortgage loans.............      
13 Investments—other (attach schedule)..........      
14 Land, buildings, and equipment: basis  
Less: accumulated depreciation (attach schedule)        
15 Other assets (describe )      
16 Total assets (to be completed by all filers—see the
instructions. Also, see page 1, item I) 1,414,445 1,385,003 1,566,971
Liabilities 17 Accounts payable and accrued expenses..........    
18 Grants payable.................    
19 Deferred revenue.................    
20 Loans from officers, directors, trustees, and other disqualified persons    
21 Mortgages and other notes payable (attach schedule)......    
22 Other liabilities (describe )    
23 Total liabilities (add lines 17 through 22)......... 0 0
Net Assets or Fund Balances Foundations that follow FASB ASC 958, check here
and complete lines 24, 25, 29 and 30.
24 Net assets without donor restrictions...........    
25 Net assets with donor restrictions............    
Foundations that do not follow FASB ASC 958, check here
and complete lines 26 through 30.
26 Capital stock, trust principal, or current funds........ 0 0
27 Paid-in or capital surplus, or land, bldg., and equipment fund 0 0
28 Retained earnings, accumulated income, endowment, or other funds 1,414,445 1,385,003
29 Total net assets or fund balances (see instructions)..... 1,414,445 1,385,003
30 Total liabilities and net assets/fund balances (see instructions). 1,414,445 1,385,003
Part III
Analysis of Changes in Net Assets or Fund Balances
1
Total net assets or fund balances at beginning of year—Part II, column (a), line 29 (must agree with end-of-year figure reported on prior year’s return) ...............
1
1,414,445
2
Enter amount from Part I, line 27a .....................
2
-29,442
3
Other increases not included in line 2 (itemize)
3
0
4
Add lines 1, 2, and 3 ..........................
4
1,385,003
5
Decreases not included in line 2 (itemize)
5
0
6
Total net assets or fund balances at end of year (line 4 minus line 5)—Part II, line 29, column (b) ..
6
1,385,003
Form 990-PF (2025)
Form 990-PF (2025)
Page 3
Part IV
Capital Gains and Losses for Tax on Investment Income
(a) List and describe the kind(s) of property sold (e.g., real estate,
2-story brick warehouse; or common stock, 200 shs. MLC Co.)		 (b)
How acquired
P—Purchase
D—Donation 		(c)
Date acquired
(mo., day, yr.) 		(d)
Date sold
(mo., day, yr.)
1 a BROWN BROS HARRIMAN   2025-01-01 2025-12-31
b CAPITAL GAINS DIVIDENDS P    
c
d
e
(e)
Gross sales price 		(f)
Depreciation allowed
(or allowable) 		(g)
Cost or other basis
plus expense of sale 		(h)
Gain or (loss)
(e) plus (f) minus (g)
a 650,165   432,433 217,732
b 15,539     15,539
c
d
e
Complete only for assets showing gain in column (h) and owned by the foundation on 12/31/69 (l)
Gains (Col. (h) gain minus
col. (k), but not less than -0-) or
Losses (from col.(h))
(i)
F.M.V. as of 12/31/69 		(j)
Adjusted basis
as of 12/31/69 		(k)
Excess of col. (i)
over col. (j), if any
a       217,732
b       15,539
c
d
e
2 Capital gain net income or (net capital loss) Bracket If gain, also enter in Part I, line 7
If (loss), enter -0- in Part I, line 7		 Bracket 2 233,271
3 Net short-term capital gain or (loss) as defined in sections 1222(5) and (6):
If gain, also enter in Part I, line 8, column (c) (see instructions). If (loss), enter -0-
in Part I, line 8 ......................... 		Bracket 3  
Part V
Excise Tax Based on Investment Income (Section 4940(a), 4940(b), 4940(e), or 4948—see instructions)
1a Exempt operating foundations described in section 4940(d)(2), check here and enter “N/A" on line 1. Bracket for line 1a
Date of ruling or determination letter:   (attach copy of letter if necessary–see instructions) 1 3,713
b All other domestic foundations enter 1.39% (0.0139) of line 27b. Exempt foreign organizations enter 4% (0.04) of Part I, line 12, col. (b)
2 Tax under section 511 (domestic section 4947(a)(1) trusts and taxable foundations only. Others enter -0-) 2 0
3 Add lines 1 and 2........................... 3 3,713
4 Subtitle A (income) tax (domestic section 4947(a)(1) trusts and taxable foundations only. Others enter -0-) 4 0
5 Tax based on investment income. Subtract line 4 from line 3. If zero or less, enter -0- ..... 5 3,713
6 Credits/Payments:
a 2025 estimated tax payments and 2024 overpayment credited to 2025 6a 1,647
b Exempt foreign organizations—tax withheld at source...... 6b 0
c Tax paid with application for extension of time to file (Form 8868)... 6c 0
d Backup withholding erroneously withheld .......... 6d 0
7 Total credits and payments. Add lines 6a through 6d.............. 7 1,647
8 Enter any penalty for underpayment of estimated tax. Check here if Form 2220 is attached. Click to see attachment
List of Attached Documents:
// Content
8 0
9 Tax due. If the total of lines 5 and 8 is more than line 7, enter amount owed....... 9 2,066
10 Overpayment. If line 7 is more than the total of lines 5 and 8, enter the amount overpaid... 10  
11 Enter the amount of line 10 to be: Credited to 2026 estimated tax   Refunded 11  
For Refunded amount, also complete and attach Form 8050. See instructions.
Form 990-PF (2025)
Form 990-PF (2025)
Page 4
Part VI-A
Statements Regarding Activities
1a
During the tax year, did the foundation attempt to influence any national, state, or local legislation or did
Yes
No
it participate or intervene in any political campaign? ....................
1a
 
No
b
Did it spend more than $100 during the year (either directly or indirectly) for political purposes? See the instructions
for the definition.................................
1b
 
No
If the answer is "Yes" to 1a or 1b, attach a detailed description of the activities and copies of any materials
published or distributed by the foundation in connection with the activities.
c
Did the foundation file Form 1120-POL for this year?.....................
1c
 
No
d
Enter the amount (if any) of tax on political expenditures (section 4955) imposed during the year:
(1) On the foundation. $ 0(2) On foundation managers.$ 0
e
Enter the reimbursement (if any) paid by the foundation during the year for political expenditure tax imposed
on foundation managers.$ 0
2
Has the foundation engaged in any activities that have not previously been reported to the IRS?.......
2
 
No
If "Yes," attach a detailed description of the activities.
3
Has the foundation made any changes, not previously reported to the IRS, in its governing instrument, articles
of incorporation, or bylaws, or other similar instruments? If "Yes," attach a conformed copy of the changes....
3
 
No
4a
Did the foundation have unrelated business gross income of $1,000 or more during the year?.........
4a
 
No
b
If "Yes," has it filed a tax return on Form 990-T for this year?...................
4b
 
 
5
Was there a liquidation, termination, dissolution, or substantial contraction during the year?.........
5
 
No
If "Yes," attach the statement required by General Instruction T.
6
Are the requirements of section 508(e) (relating to sections 4941 through 4945) satisfied either:
round bullet By language in the governing instrument, or
round bullet By state legislation that effectively amends the governing instrument so that no mandatory directions
that conflict with the state law remain in the governing instrument? ................
6
Yes
 
7
Did the foundation have at least $5,000 in assets at any time during the year? If "Yes," complete Part II, col. (c),
and Part XIV..................................
7
Yes
 
8a
Enter the states to which the foundation reports or with which it is registered (see instructions)
MA
b
If the answer is "Yes" to line 7, has the foundation furnished a copy of Form 990-PF to the Attorney
General (or designate) of each state as required by General Instruction G? If "No," attach explanation .
8b
Yes
 
9
Is the foundation claiming status as a private operating foundation within the meaning of section 4942(j)(3)
or 4942(j)(5) for calendar year 2025 or the taxable year beginning in 2025? See the instructions for Part XIII.
If "Yes," complete Part XIII .............................
9
 
No
10
Did any persons become substantial contributors during the tax year? If "Yes," attach a schedule listing their names
and addresses. Click to see attachment
List of Attached Documents:
// Content
...............................
10
Yes
 
11
At any time during the year, did the foundation, directly or indirectly, own a controlled entity within the
meaning of section 512(b)(13)? If "Yes," attach schedule. See instructions .............
11
 
No
12
Did the foundation make a distribution to a donor advised fund over which the foundation or a disqualified person had
advisory privileges? If "Yes," attach statement. See instructions.................
12
 
No
13
Did the foundation comply with the public inspection requirements for its annual returns and exemption application?
13
Yes
 
Website addressN/A
14
The books are in care ofWALTER CELIA GILBERT Telephone no. (617) 864-8778

Located at15 GRAY GARDENS WESTCAMBRIDGEMA ZIP+402138
15
Section 4947(a)(1) nonexempt charitable trusts filing Form 990-PF in lieu of Form 1041 —check here .........
and enter the amount of tax-exempt interest received or accrued during the year ........
15
 
16 At any time during calendar year 2025, did the foundation have an interest in or a signature or other authority over YesNo
a bank, securities, or other financial account in a foreign country? .................
16   No
See the instructions for exceptions and filing requirements for FinCEN Form 114. If "Yes", enter the name of the foreign
country
Form 990-PF (2025)
Form 990-PF (2025)
Page 5
Part VI-B
Statements Regarding Activities for Which Form 4720 May Be Required
File Form 4720 if any item is checked in the "Yes" column, unless an exception applies.
Yes
No
1a
During the year did the foundation (either directly or indirectly):
(1) Engage in the sale or exchange, or leasing of property with a disqualified person? ...........
1a(1)
 
No
(2) Borrow money from, lend money to, or otherwise extend credit to (or accept it from)
a disqualified person? ..............................
1a(2)
 
No
(3) Furnish goods, services, or facilities to (or accept them from) a disqualified person? ...........
1a(3)
 
No
(4) Pay compensation to, or pay or reimburse the expenses of, a disqualified person? ............
1a(4)
 
No
(5) Transfer any income or assets to a disqualified person (or make any of either available
for the benefit or use of a disqualified person)? ......................
1a(5)
 
No
(6) Agree to pay money or property to a government official? (Exception. Check "No"
if the foundation agreed to make a grant to or to employ the official for a period
after termination of government service, if terminating within 90 days.) ...............
1a(6)
 
No
b
If any answer is "Yes" to 1a(1)–(6), did any of the acts fail to qualify under the exceptions described in Regulations
section 53.4941(d)-3 or in a current notice regarding disaster assistance? See instructions ..........
1b
 
 
c
Organizations relying on a current notice regarding disaster assistance check here ........
d
Did the foundation engage in a prior year in any of the acts described in 1a, other than excepted acts,
that were not corrected before the first day of the tax year beginning in 2025? .............
1d
 
No
2
Taxes on failure to distribute income (section 4942) (does not apply for years the foundation was a private
operating foundation defined in section 4942(j)(3) or 4942(j)(5)):
a
At the end of tax year 2025, did the foundation have any undistributed income (Part XII, lines 6d
and 6e) for tax year(s) beginning before 2025?....................
2a
 
No
If "Yes," list the years 20, 20, 20, 20
b
Are there any years listed in 2a for which the foundation is not applying the provisions of section 4942(a)(2)
(relating to incorrect valuation of assets) to the year’s undistributed income? (If applying section 4942(a)(2)
to all years listed, answer "No" and attach statement—see instructions.) ..............
2b
 
 
c
If the provisions of section 4942(a)(2) are being applied to any of the years listed in 2a, list the years here.
20, 20, 20, 20
3a
Did the foundation hold more than a 2% direct or indirect interest in any business enterprise at
any time during the year? ..............................
3a
 
No
b
If "Yes," did it have excess business holdings in 2025 as a result of (1) any purchase by the foundation
or disqualified persons after May 26, 1969; (2) the lapse of the 5-year period (or longer period approved
by the Commissioner under section 4943(c)(7)) to dispose of holdings acquired by gift or bequest; or (3)
the lapse of the 10-, 15-, or 20-year first phase holding period? (Use Form 4720, Schedule C, to determine
if the foundation had excess business holdings in 2025.).....................
3b
 
 
4a
Did the foundation invest during the year any amount in a manner that would jeopardize its charitable purposes?
4a
 
No
b
Did the foundation make any investment in a prior year (but after December 31, 1969) that could jeopardize its
charitable purpose that had not been removed from jeopardy before the first day of the tax year beginning in 2025? ..
4b
 
No
Form 990-PF (2025)
Form 990-PF (2025)
Page 6
Part VI-B
Statements Regarding Activities for Which Form 4720 May Be Required (continued)
5a
During the year did the foundation pay or incur any amount to:
Yes
No
(1) Carry on propaganda, or otherwise attempt to influence legislation (section 4945(e))? ..........
5a(1)
 
No
(2) Influence the outcome of any specific public election (see section 4955); or to carry
on, directly or indirectly, any voter registration drive? ....................
5a(2)
 
No
(3) Provide a grant to an individual for travel, study, or other similar purposes? .............
5a(3)
 
No
(4) Provide a grant to an organization other than a charitable, etc., organization described
in section 4945(d)(4)(A)? See instructions ........................
5a(4)
 
No
(5) Provide for any purpose other than religious, charitable, scientific, literary, or
educational purposes, or for the prevention of cruelty to children or animals? .............
5a(5)
 
No
b
If any answer is "Yes" to 5a(1)–(5), did any of the transactions fail to qualify under the exceptions described in
Regulations section 53.4945 or in a current notice regarding disaster assistance? See instructions ........
5b
 
 
c
Organizations relying on a current notice regarding disaster assistance check .........
d
If the answer is "Yes" to question 5a(4), does the foundation claim exemption from the
tax because it maintained expenditure responsibility for the grant? .................
5d
 
 
If "Yes," attach the statement required by Regulations section 53.4945–5(d).
6a
Did the foundation, during the year, receive any funds, directly or indirectly, to pay premiums on
a personal benefit contract? .............................
6a
 
No
b
Did the foundation, during the year, pay premiums, directly or indirectly, on a personal benefit contract? ....
6b
 
No
If "Yes" to 6b, file Form 8870.
7a
At any time during the tax year, was the foundation a party to a prohibited tax shelter transaction?
7a
 
No
b
If "Yes", did the foundation receive any proceeds or have any net income attributable to the transaction? .....
7b
 
 
8
Is the foundation subject to the section 4960 tax on payment(s) of more than $1,000,000 in remuneration or
excess parachute payment during the year? .........................
8
 
No
Part VII
Information About Officers, Directors, Trustees, Foundation Managers, Highly Paid Employees,
and Contractors
1 List all officers, directors, trustees, foundation managers and their compensation. See instructions
(a) Name and address (b) Title, and average
hours per week
devoted to position 		(c) Compensation
 (If not paid, enter
-0-) 		(d) Contributions to employee benefit plans and deferred compensation (e) Expense account,
other allowances
WALTER GILBERT TRUSTEE
0.00 		0 0 0
15 GRAY GARDENS WEST
CAMBRIDGE,MA02138
CELIA GILBERT TRUSTEE
0.00 		0 0 0
15 GRAY GARDENS WEST
CAMBRIDGE,MA02138
KATE GILBERT TRUSTEE
0.00 		0 0 0
112 LEXINGTON AVE
CAMBRIDGE,MA021383368
ERIC DOMESHEK TRUSTEE
0.00 		0 0 0
112 LEXINGTON AVE
CAMBRIDGE,MA021383368
JOHN R GILBERT TRUSTEE
0.00 		0 0 0
1 FITCHBURG ST UNIT C-107
SOMERVILLE,MA02143
VALERIE LEITER TRUSTEE
0.00 		0 0 0
1 FITCHBURG ST UNIT C-107
SOMERVILLE,MA02143
2 Compensation of five highest-paid employees (other than those included on line 1—see instructions). If none, enter “NONE."
(a) Name and address of each employee paid more than $50,000 (b) Title, and average
hours per week
devoted to position 		(c) Compensation (d) Contributions to
employee benefit
plans and deferred
compensation 		(e) Expense account,
other allowances
NONE
Total number of other employees paid over $50,000................... 0
Form 990-PF (2025)
Form 990-PF (2025)
Page 7
Part VII
Information About Officers, Directors, Trustees, Foundation Managers, Highly Paid Employees,
and Contractors (continued)
3 Five highest-paid independent contractors for professional services (see instructions). If none, enter "NONE".
(a) Name and address of each person paid more than $50,000 (b) Type of service (c) Compensation
NONE
Total number of others receiving over $50,000 for professional services.............right arrow0
Part VIII-A
Summary of Direct Charitable Activities
List the foundation’s four largest direct charitable activities during the tax year. Include relevant statistical information such as the number of organizations and other beneficiaries served, conferences convened, research papers produced, etc. Expenses
1  
2  
3  
4  
Part VIII-B
Summary of Program-Related Investments (see instructions)
Describe the two largest program-related investments made by the foundation during the tax year on lines 1 and 2. Amount
1  
2  
All other program-related investments. See instructions.
3  
Total. Add lines 1 through 3.........................0
Form 990-PF (2025)
Form 990-PF (2025)
Page 8
Part IX
Minimum Investment Return (All domestic foundations must complete this part. Foreign foundations, see instructions.)
1
Fair market value of assets not used (or held for use) directly in carrying out charitable, etc.,
purposes:
a
Average monthly fair market value of securities...................
1a
1,663,448
b
Average of monthly cash balances.......................
1b
56,003
c
Fair market value of all other assets (see instructions)................
1c
0
d
Total (add lines 1a, 1b, and 1c).......................
1d
1,719,451
e
Reduction claimed for blockage or other factors reported on lines 1a and
1c (attach detailed explanation) .............
1e
0
2
Acquisition indebtedness applicable to line 1 assets..................
2
0
3
Subtract line 2 from line 1d.........................
3
1,719,451
4
Cash deemed held for charitable activities. Enter 1.5% (0.015) of line 3 (for greater amount, see
instructions) .............................
4
25,792
5
Net value of noncharitable-use assets. Subtract line 4 from line 3. ............
5
1,693,659
6
Minimum investment return. Enter 5% (0.05) of line 5 ................
6
84,683
Part X
Distributable Amount (see instructions) (Section 4942(j)(3) and (j)(5) private operating foundations and certain foreign organizations check here and do not complete this part.)
1
Minimum investment return from Part IX, line 6..................
1
84,683
2a
Tax on investment income for 2025 from Part V, line 5 .......
2a
3,713
b
Income tax for 2025. (This does not include the tax from Part V.) ...
2b
 
c
Add lines 2a and 2b............................
2c
3,713
3
Distributable amount before adjustments. Subtract line 2c from line 1............
3
80,970
4
Recoveries of amounts treated as qualifying distributions................
4
0
5
Add lines 3 and 4............................
5
80,970
6
Deduction from distributable amount (see instructions) .................
6
0
7
Distributable amount as adjusted. Subtract line 6 from line 5. Enter here and on Part XII, line 1 ...
7
80,970
Part XI
Qualifying Distributions (see instructions)
1
Amounts paid (including administrative expenses) to accomplish charitable, etc., purposes:
a
Expenses, contributions, gifts, etc.—total from Part I, line 26, column (d) ..........
1a
296,035
b
Program-related investments—total from Part VIII-B..................
1b
0
2
Amounts paid to acquire assets used (or held for use) directly in carrying out charitable, etc.,
purposes...............................
2
 
3
Amounts set aside for specific charitable projects that satisfy the:
a
Suitability test (prior IRS approval required)....................
3a
 
b
Cash distribution test (attach the required schedule) .................
3b
 
4
Qualifying distributions. Add lines 1a through 3b. Enter here and on Part XII, line 4. .......
4
296,035
Form 990-PF (2025)
Form 990-PF (2025)
Page 9
Part XII
Undistributed Income (see instructions)
(a)
Corpus 		(b)
Years prior to 2024 		(c)
2024 		(d)
2025
1 Distributable amount for 2025 from Part X, line 7 80,970
2 Undistributed income, if any, as of the end of 2025:
a Enter amount for 2024 only....... 0
b Total for prior years:20 , 20, 20 0
3 Excess distributions carryover, if any, to 2025:
a From 2020...... 73,596
b From 2021...... 197,574
c From 2022...... 95,437
d From 2023...... 243,521
e From 2024...... 104,746
f Total of lines 3a through e ........ 714,874
4Qualifying distributions for 2025 from Part
XI, line 4: $ 296,035
a Applied to 2024, but not more than line 2a 0
b Applied to undistributed income of prior years
(Election required—see instructions) ..... 		0
c Treated as distributions out of corpus (Election
required—see instructions) ........ 		0
d Applied to 2025 distributable amount..... 80,970
e Remaining amount distributed out of corpus 215,065
5 Excess distributions carryover applied to 2025. 0 0
(If an amount appears in column (d), the
same amount must be shown in column (a).)
6Enter the net total of each column as
indicated below:
a Corpus. Add lines 3f, 4c, and 4e. Subtract line 5 929,939
b Prior years’ undistributed income. Subtract
line 4b from line 2b .......... 		0
c Enter the amount of prior years’ undistributed
income for which a notice of deficiency has
been issued, or on which the section 4942(a)
tax has been previously assessed...... 		0
d Subtract line 6c from line 6b. Taxable amount
—see instructions ........... 		0
e Undistributed income for 2024. Subtract line
4a from line 2a. Taxable amount—see
instructions ............. 		0
f Undistributed income for 2025. Subtract
lines 4d and 5 from line 1. This amount must
be distributed in 2026 .......... 		0
7 Amounts treated as distributions out of
corpus to satisfy requirements imposed by
section 170(b)(1)(F) or 4942(g)(3) (Election may
be required - see instructions) ....... 		0
8 Excess distributions carryover from 2020 not
applied on line 5 or line 7 (see instructions) ... 		73,596
9 Excess distributions carryover to 2026.
Subtract lines 7 and 8 from line 6a ...... 		856,343
10 Analysis of line 9:
a Excess from 2021 .... 197,574
b Excess from 2022 .... 95,437
c Excess from 2023 .... 243,521
d Excess from 2024 .... 104,746
e Excess from 2025 .... 215,065
Form 990-PF (2025)
Form 990-PF (2025)
Page 10
Part XIII
Private Operating Foundations (see instructions and Part VI-A, question 9)
1a If the foundation has received a ruling or determination letter that it is a private operating
foundation, and the ruling is effective for 2025, enter the date of the ruling ......
 
b Check box to indicate whether the organization is a private operating foundation described in section or
2a Enter the lesser of the adjusted net
income from Part I or the minimum
investment return from Part IX for each
year listed .......... 		Tax year Prior 3 years (e) Total
(a) 2025 (b) 2024 (c) 2023 (d) 2022
         
b 85% (0.85) of line 2a .......          
c Qualifying distributions from Part XI,
line 4 for each year listed ..... 		         
d Amounts included in line 2c not used directly
for active conduct of exempt activities .......... 		         
e Qualifying distributions made directly
for active conduct of exempt activities.
Subtract line 2d from line 2c .... 		         
3 Complete 3a, 3b, or 3c for the
alternative test relied upon:
a “Assets" alternative test—enter:
(1) Value of all assets ......          
(2) Value of assets qualifying
under section 4942(j)(3)(B)(i)		          
b “Endowment" alternative test— enter 2/3
of minimum investment return shown in
Part IX, line 6 for each year listed .. 		         
c “Support" alternative test—enter:
(1) Total support other than gross
investment income (interest,
dividends, rents, payments
on securities loans (section
512(a)(5)), or royalties) .... 		         
(2) Support from general public
and 5 or more exempt
organizations as provided in
section 4942(j)(3)(B)(iii).... 		         
(3) Largest amount of support
from an exempt organization		          
(4) Gross investment income          
Part XIV
Supplementary Information (Complete this part only if the foundation had $5,000 or more in
assets at any time during the year—see instructions.)
1Information Regarding Foundation Managers:
aList any managers of the foundation who have contributed more than 2% of the total contributions received by the foundation
before the close of any tax year (but only if they have contributed more than $5,000). (See section 507(d)(2).)
bList any managers of the foundation who own 10% or more of the stock of a corporation (or an equally large portion of the
ownership of a partnership or other entity) of which the foundation has a 10% or greater interest.
2Information Regarding Contribution, Grant, Gift, Loan, Scholarship, etc., Programs:
Check here if the foundation only makes contributions to preselected charitable organizations and does not accept
unsolicited requests for funds. If the foundation makes gifts, grants, etc. to individuals or organizations under
other conditions, complete items 2a, 2b, 2c, and 2d. See instructions
aThe name, address, and telephone number or email address of the person to whom applications should be addressed:
bThe form in which applications should be submitted and information and materials they should include:
cAny submission deadlines:
dAny restrictions or limitations on awards, such as by geographical areas, charitable fields, kinds of institutions, or other
factors:
Form 990-PF (2025)
Form 990-PF (2025)
Page 11
Part XIV
Supplementary Information (continued)
3 Grants and Contributions Paid During the Year or Approved for Future Payment
Recipient If recipient is an individual,
show any relationship to
any foundation manager
or substantial contributor
 Foundation
status of
recipient 		Purpose of grant or
contribution 		Amount
Name and address (home or business)
aPaid during the year

ANCIENT EGYPT RESEARCH ASSOCIATES

26 LINCOLN ST STE 5
BOSTON,MA02135 		NONE   UNRESTRICTED 100,000

BETH ISRAEL DEACONESS MEDICAL CENTER

330 BROOKLINE AVE
BOSTON,MA02215 		NONE   UNRESTRICTED 60,000

COLD SPRING HARBOR LABORATORY

1 BUNGTOWN RD
COLD SPRING HARBOR,NY11724 		NONE   UNRESTRICTED 40,000

HARVARD ART MUSEUM

32 QUINCY STREET
CAMBRIDGE,MA02138 		NONE   UNRESTRICTED 15,000

MUSEUM OF FINE ARTS

465 HUNTINGTON AVE
BOSTON,MA02115 		NONE   UNRESTRICTED 56,000

SOCIETY FOR SCIENCE AND THE PUBLIC

1719 N STREET NW
WASHINGTON,DC20036 		NONE   UNRESTRICTED 25,000
Total ................................. 3a 296,000
bApproved for future payment
Total ................................. 3b 0
Form 990-PF (2025)
Form 990-PF (2025)
Page 12
Part XV-A
Analysis of Income-Producing Activities
Enter gross amounts unless otherwise indicated. Unrelated business income Excluded by section 512, 513, or 514 (e)
Related or exempt
function income
(See instructions.)
1Program service revenue: (a)
Business code 		(b)
Amount 		(c)
Exclusion code 		(d)
Amount
a
b
c
d
e
f
gFees and contracts from government agencies          
2 Membership dues and assessments ....          
3 Interest on savings and temporary cash
investments ........... 		         
4 Dividends and interest from securities ....     14 47,919  
5 Net rental income or (loss) from real estate:
aDebt-financed property......          
bNot debt-financed property.....          
6 Net rental income or (loss) from personal property          
7 Other investment income .....          
8 Gain or (loss) from sales of assets other than
inventory ............ 		    14 233,271  
9 Net income or (loss) from special events:          
10 Gross profit or (loss) from sales of inventory          
11 Other revenue:
a
b
c
d
e
12 Subtotal. Add columns (b), (d), and (e) .. 0 281,190 0
13Total. Add line 12, columns (b), (d), and (e)..................
13
281,190
(See worksheet in line 13 instructions to verify calculations.)
Part XV-B
Relationship of Activities to the Accomplishment of Exempt Purposes
Line No.
DownArrow 		Explain below how each activity for which income is reported in column (e) of Part XV-A contributed importantly to
the accomplishment of the foundation’s exempt purposes (other than by providing funds for such purposes). (See
instructions.)
Form 990-PF (2025)
Form 990-PF (2025)
Page 13
Part XVI
Information Regarding Transfers To and Transactions and Relationships With Noncharitable Exempt Organizations
1
Did the organization directly or indirectly engage in any of the following with any other organization described in section 501(c) (other than section 501(c)(3) organizations) or in section 527, relating to political organizations?
Yes
No
a
Transfers from the reporting foundation to a noncharitable exempt organization of:
(1) Cash...................................
1a(1)
 
No
(2) Other assets.................................
1a(2)
 
No
b
Other transactions:
(1) Sales of assets to a noncharitable exempt organization....................
1b(1)
 
No
(2) Purchases of assets from a noncharitable exempt organization..................
1b(2)
 
No
(3) Rental of facilities, equipment, or other assets.......................
1b(3)
 
No
(4) Reimbursement arrangements...........................
1b(4)
 
No
(5) Loans or loan guarantees.............................
1b(5)
 
No
(6) Performance of services or membership or fundraising solicitations................
1b(6)
 
No
c
Sharing of facilities, equipment, mailing lists, other assets, or paid employees..............
1c
 
No
d
If the answer to any of the above is "Yes," complete the following schedule. Column (b) should always show the fair market value
of the goods, other assets, or services given by the reporting foundation. If the foundation received less than fair market value
in any transaction or sharing arrangement, show in column (d) the value of the goods, other assets, or services received.
(a) Line No. (b) Amount involved (c) Name of noncharitable exempt organization (d) Description of transfers, transactions, and sharing arrangements
2a
Is the foundation directly or indirectly affiliated with, or related to, one or more tax-exempt organizations
described in section 501(c) (other than section 501(c)(3)) or in section 527? ...........
b
If "Yes," complete the following schedule.

(a) Name of organization (b) Type of organization (c) Description of relationship
Sign Here
Under penalties of perjury, I declare that I have examined this return, including accompanying schedules and statements, and to the best of my knowledge and belief, it is true, correct, and complete. Declaration of preparer (other than taxpayer) is based on all information of which preparer has any knowledge.
May the IRS discuss this return
with the preparer shown below?
See instructions.
Signature of officer or trustee Date Title
Paid Preparer Use Only Preparer's name Preparer's Signature Date Check if self-
employed 		PTIN
Firm's name
Firm's EIN
Firm's address


Phone no.
Form 990-PF (2025)
Additional Data


Software ID:  
Software Version:  


Form 990PF - Special Condition Description:
Special Condition Description

TY 2025 InvestmentsCorpStockSchedule
Name:
THE RIVER FOUNDATION
 
C/O WALTER & CELIA GILBERT TRUSTEES
EIN:
04-3254488
Name of Stock End of Year Book Value End of Year Fair Market Value
MARKETABLE SECURITIES 1,361,766 1,543,862

TY 2025 OtherProfessionalFeesSchedule
Name:
THE RIVER FOUNDATION
 
C/O WALTER & CELIA GILBERT TRUSTEES
EIN:
04-3254488
Category Amount Net Investment Income Adjusted Net Income Disbursements for Charitable Purposes
OTHER PROFESSIONAL 9,754 9,754   0
ACCOUNTING FEES 4,305 4,305   0


TY 2025 SubstantialContributorsSch
Name:
THE RIVER FOUNDATION
 
C/O WALTER & CELIA GILBERT TRUSTEES
EIN:
04-3254488
Name Address
WALTER AND CELIA GILBERT 15 GRAY GARDENS WEST
CAMBRIDGE,MA02138


TY 2025 TaxesSchedule
Name:
THE RIVER FOUNDATION
 
C/O WALTER & CELIA GILBERT TRUSTEES
EIN:
04-3254488
Category Amount Net Investment Income Adjusted Net Income Disbursements for Charitable Purposes
COMM OF MASS 35 0   35
FOREIGN TAXES 538 0   0