In 1957, when Fortune prepared its first list of the wealthiest Americans, it estimated that Ailsa Mellon Bruce, her brother, Paul, and her cousins Sarah Mellon and Richard King Mellon were all amongst the richest eight people in the United States, with fortunes of between 400 and 700 million dollars each..
Bruce established the Avalon Foundation in 1940, which made grants to colleges and universities, medical schools and hospitals, youth programs and community services, churches, environmental projects, and an array of cultural and arts organizations.
She married David K. E. Bruce in 1926, a scion of a prominent Virginia family; he also would become United States Ambassador to the United Kingdom (1961-69). They divorced in 1945. When their only child, Audrey, and her husband, Stephen Currier, died in a presumed plane crash in 1967 leaving three young children—Andrea, Lavinia, and Michael—Ailsa Bruce decided to bequeath her collection of 18th-century English furniture and ceramics to the Carnegie Institute of Pittsburgh, Pennsylvania.
At her death in 1969, Ailsa Bruce bequeathed 153 paintings, primarily by French artists, to the National Gallery of Art, as well as establishing a fund for future acquisitions.