Winslow Foundation



Tax ID:


Tax-Exempt Status:


Budget (2015):

Revenue: $2,523,746
Expenses: $1,992,681
Assets: $26,395,067




Wren Winslow Wirth

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The Winslow Foundation is a private foundation that funds primarily left-leaning nonprofit organizations, especially environmentalist groups. Wren Winslow Wirth, the wife of Democratic politician, longtime United Nations Foundation president, former U.S. Senator from Colorado, and Clinton administration State Department official Tim Wirth, heads the foundation. 1

According to left-leaning philanthropic resource Inside Philanthropy, the Winslow Foundation “maintains a low public profile, does not have a website, and employs a small formal staff of just three people.” 2


The Winslow Foundation principally supports left-progressive environmentalist groups. In 2018, it funded the League of Conservation Voters Education Fund, Sunrise Movement Education Fund, Sustainable Markets Foundation, Virginia Organizing, and WildEarth Guardians. It further gave $250,000 to Mothers Out Front, a left-progressive environmentalist group founded by Kelsey Wirth, Wren Winslow and Tim Wirth’s daughter and a member of the Winslow Foundation board. 3

Wirth Family

Wren Winslow Wirth is the president of the Winslow Foundation. Wren is married to Tim Wirth, a Democratic politician who served in the U.S. House of Representatives from 1975 until 1987 and the U.S. Senate from 1987 until 1993. Tim Wirth then held the position of Undersecretary of State for Democracy and Global Affairs during the Clinton administration. 4

Kelsey Wirth, the daughter of Tim and Wren, is a vice president and trustee of the foundation. She holds an MBA from Stanford University and is the founder of Mothers Out Front, a left-leaning alliance of mothers and grandmothers who advocate for environmentalist policy including the socialist Green New Deal. Kelsey is also the co-founder of Align Technology, a company that provides alternative materials for orthodontics. 5

Christopher Wirth, the son to Tim and Wren, is a vice president and trustee of the foundation. Tim is also the founder of Liberty Puzzles. 6


  1. Greene, David L. “Giving $1 Billion to the World Donation: Former U.S. Sen. Timothy Wirth of Colorado Must Distribute the Lavish Donation of His Longtime Friend, Media Mogul Ted Turner. He Calls It His Toughest Task.” Baltimore Sun, July 29, 1998.
  2. Moses, Sue-Lynn. “Winslow Foundation: Grants for Environmental Conservation.” Inside Philanthropy. Inside Philanthropy, May 2, 2019.
  3. Winslow Foundation, Return of a Private Foundation (Form 990-PF), 2018, Part XV Line 3
  4. “Tim Wirth.” Center of the American West Tim Wirth Comments. Accessed May 11, 2020.
  5. Tindera, Michela. “Out Of Silicon Valley, A Billion-Dollar Orthodontics Business Built With Plastic And Patents.” Forbes. Forbes Magazine, April 26, 2017.
  6. “A Piece of History.” Liberty Puzzles. Accessed May 11, 2020.

Donation Recipients

  1. (National) (Non-profit)
  2. Alaska Conservation Foundation (Non-profit)
  3. Alliance for Global Justice (AFGJ) (Non-profit)
  4. Appalachian Voices (Non-profit)
  5. Better Future Project (Non-profit)
  6. Blue Frontier Campaign (Non-profit)
  7. Catskill Mountainkeeper (Non-profit)
  8. Center for Public Interest Research (Non-profit)
  9. Centre for International Governance Innovation (Other Group)
  10. Civil Society Institute (Non-profit)
  11. Columbia University (Non-profit)
  12. Conservation Colorado Education Fund (Non-profit)
  13. El Puente de Williamsburg (Non-profit)
  14. Environmental Working Group (EWG) (Non-profit)
  15. Friends of United Nations Fund for Population Activities (UNFPA) (Non-profit)
  16. Government Accountability Project (GAP) (Non-profit)
  17. Grist Magazine (Non-profit)
  18. Harvard University (Non-profit)
  19. Institute for Energy Economics and Financial Analysis (Non-profit)
  20. Kentucky Coalition (Non-profit)
  21. Mothers Out Front (Non-profit)
  22. NARAL Pro-Choice America Foundation (Non-profit)
  23. National Parks Conservation Association (Non-profit)
  24. Ohio Citizen Action Education Fund (Non-profit)
  25. Open Space Institute (Non-profit)
  26. Pinelands Preservation Alliance (Non-profit)
  27. Population Media Center (Non-profit)
  28. Rainforest Action Network (RAN) (Non-profit)
  29. Regeneration Project (Non-profit)
  30. Rockefeller Family Fund (Non-profit)
  31. Southern Utah Wilderness Alliance (Non-profit)
  32. Sunrise Movement Education Fund (Non-profit)
  33. Sustainable Markets Foundation (Non-profit)
  34. Tides Center (Non-profit)
  35. Virginia Organizing (Non-profit)
  36. Western Resource Advocates (Non-profit)
  37. WildAid (Non-profit)
  38. WildEarth Guardians (Non-profit)
  39. Women’s Earth and Climate Caucus (Non-profit)
  40. Woods Hole Research Center (Non-profit)
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Nonprofit Information

  • Accounting Period: December - November
  • Tax Exemption Received: September 1, 1987

  • Available Filings

    Period Form Type Total revenue Total functional expenses Total assets (EOY) Total liabilities (EOY) Unrelated business income? Total contributions Program service revenue Investment income Comp. of current officers, directors, etc. Form 990
    2015 Dec Form PF $2,523,746 $1,992,681 $26,395,067 $0 $0 $0 $0 $0 PDF
    2014 Dec Form PF $1,862,133 $1,757,433 $27,216,696 $18,000 $0 $0 $0 $0 PDF
    2013 Dec Form PF $2,363,601 $1,765,345 $27,130,246 $36,250 $0 $0 $0 $0 PDF
    2012 Dec Form PF $1,339,685 $1,546,658 $26,556,524 $60,784 $0 $0 $0 $0 PDF
    2011 Dec Form PF $895,480 $1,857,103 $26,808,835 $27,669 $0 $0 $0 $0 PDF

    Additional Filings (PDFs)

    Winslow Foundation

    WILMINGTON, DE 19809-0000