MCF was established in 1986 with the assets of a trust from long time Marin County residents, Leonard and Beryl H. Buck. As of 2023, he organization has $3 billion in assets, the sixth largest amount among the nation’s community foundations. About $1 billion is the product of the original Beryl Buck endowment, while the rest involves “donor-advised funds.” Over 350 individuals, families, businesses, and community groups have established funds at MCF. Grants made from these funds support a wide range of issues within Marin County, elsewhere in the U.S., and around the world. MCF is governed by a nine-member Board of Trustees along with its President and CEO. When MCF was started, three Major Projects — the Buck Institute for Age Research, the Buck Institute for Education, and Marin Institute — were established under the Foundation's umbrella. In March 2016, the foundation reconfigured its organizational structure into a two-tier structure. The board at the time created a new board to which it ceded control.