John D. and Catherine T. MacArthur Foundation

John D. MacArthur owned Bankers Life and Casualty and other businesses, as well as considerable property holdings in Florida and New York. His wife, Catherine, held positions in many of these companies. Their attorney, William T. Kirby, and Paul Doolen, their chief financial officer, suggested that the family create a foundation to be endowed by their vast fortune.

When MacArthur died on January 6, 1978, he was worth in excess of a billion dollars. He left 92 percent of his estate to found the John D. and Catherine T. MacArthur Foundation. Its first board of directors, per MacArthur's will, also included J. Roderick MacArthur, John's son from his first marriage, two other officers of Bankers Life and Casualty, and radio commentator Paul Harvey. Jonas Salk, the inventor of the polio vaccine, later joined the board of directors.

The elder MacArthur believed in the free market. However, he did not direct how foundation money was to be spent after he died. MacArthur told the board of directors, "I figured out how to make the money. You fellows will have to figure out how to spend it."

Between 1979 and 1981, John's son, an ideological opponent of his father with whom the elder MacArthur had an acrimonious relationship, waged a legal battle against the foundation for control of the board of directors. The younger MacArthur sued eight members of the board, accusing them of mismanagement of the foundation funds. These court cases were dismissed by each jurisdiction for lack of merit.

In 1984, MacArthur again sued the board of directors including William Kirby, his father's trusted attorney, asking a Cook County circuit court to liquidate the entire MacArthur Foundation. He dropped the suit later that year when he was diagnosed with pancreatic cancer.

In March 2025, the foundation announced plans to increase its giving to at least six percent of its endowment in response to the Trump administration's efforts to cut federal funding and programs. Citing that grantees receive 12 percent of their funding from government grants, MacArthur Foundation President John Palfrey said, "Our goal is to lessen negative impacts and risks of the current, man-made emergency and to help our grantees deliver on their mission."