The Marguerite Casey Foundation is the smaller of the two major left-of-center private foundations created from the legacy of United Parcel Service founder James E. Casey, the other being the Annie E. Casey Foundation. The Marguerite Casey Foundation emerged nearly two decades after James E. Casey’s death from Casey Family Programs, a project Casey had formed to provide foster care services in the Pacific Northwest. The Foundation is notable for its support of left-of-center community organizing, including the now-defunct ACORN network.
In 1999 UPS made its Initial Public Offering, doubling the size of the Casey Family Programs endowment. Casey Family Programs, an operating foundation, decided to use this windfall to create a private foundation as a spinoff. The Marguerite Casey Foundation began as a division of Casey Family Programs in 2001 and became independent in 2010.
The foundation is named after James E. Casey’s sister, Marguerite Casey, a long-time member of the Casey Family Programs board. Marguerite Casey was not involved in the creation of the foundation.
From its start, the Marguerite Casey Foundation has given money to leftist organizations. In 2005 the Sarasota Herald-Tribune reported that the foundation had given several grants to the controversial community and labor organizing group ACORN, and ACORN then transferred the funds to Walmart Alliance for Reform Now, which encouraged Walmart employees to quit and collect unemployment if their schedules shifted or their hours were cut.  The Marguerite Casey Foundation ultimately gave ACORN $4 million before the organization’s dissolution in 2009; National Public Radio correspondent Pam Fessler reported in 2009 that “the foundation thinks ACORN has done some outstanding work for the poor.” 
The New York Times reported in 2014 that a report from the U.S. Chamber of Commerce found that the Marguerite Casey Foundation from 2009 through 2012 donated $300,000 to the Southwest Workers Union and $300,000 to the Coalition of Immokalee Workers. 
In 2008, the Marguerite Casey Foundation donated $6 million (with Casey Family Programs adding $1 million more) to support Equal Voices for America’s Families, which held a national convention in Los Angeles, Chicago, and Birmingham, Alabama in which 15,000 people met to demand that the government increase subsidies for child care, health insurance, and early childhood education as well as a substantial increase in the minimum wage.  The Marguerite Casey Foundation also was the primary backer of a second Equal Voices for America convention held in 2012. 
In a 2015 article for Foundation Watch, Tom Johnson reported that the Marguerite Casey Foundation had given NEO Philanthropy $1.5 million since 2005; NEO Philanthropy has been described as “the Left’s ‘dark money’ coordinator of choice.” 
The Washington Free Beacon in 2017 profiled Center for Community Change Action, a 501(c)(4) affiliated with the Center for Community Change which the website reported “has been associated with anti-Trump campaigns for some time now.” The website obtained an unredacted copy of the Center for Community Change’s 2015 tax return and said that the Marguerite Casey Foundation gave the center $515,000 in that year, with seven-figure grants to the center coming from the Ford, Kellogg, and Open Society Foundations. 
The Marguerite Casey Foundation also founded Equal Voice Action, a 501(c)(4) which the Chronicle of Philanthropy reported in 2019 aimed “to build a movement enabling poor people to exercise political power.” According to the foundation, the goal of Equal Voice America is to create a “movement to win better wages, improvements in criminal-justice systems, changes in health care, LGBT rights, better schools, and immigration reforms.” The Marguerite Casey Foundation has given Equal Voice America a steady stream of grants, including $1.1 million in 2017. 
The Chronicle of Philanthropy reported that “An unfettered debate about Equal Voice Action never happened inside the foundation because everyone knew that it was a priority” for the foundation’s president, Luz Vega-Marquis. 
In 2019 the Marguerite Casey Foundation was the primary supporter of the National Antiracist Book Festival, sponsored by American University. Ibram X. Kendi, director of the university’s Antiracist Research and Policy Center, stated the event “will offer one of the most distinguished lineups of antiracist authors ever assembled for a book festival,” adding that his goal was to attract readers “striving to make sense of the presidency of Barack Obama, police violence, Black Lives Matter, immigration battles, Confederate monuments, white nationalist organizing, and Donald Trump, among other topics.” Among the authors at the forum were two MacArthur Fellows, Harvard professor Henry Louis Gates and Yale poetry professor Claudia Rankine, as well as civil rights activist DeRay Mckesson. 
Luz Vega-Marquis, the Marguerite Casey Foundation’s president since its formation, announced in 2019 that she would retire in 2020.  Vega-Marquis had faced criticism from anonymous employees on the website Glassdoor for an “autocratic” management style; the Chronicle of Philanthropy reported that stories about the unpleasant workplace environment made it more difficult for the Marguerite Casey Foundation to hire staff.