Cargill was one of eight heirs to the Minneapolis-based grain-trading conglomerate Cargill, Forbes Magazine listed her in 2005 as the 164th richest American, with a net worth of $1.8 billion. She was a major donor to the American Red Cross, the Nature Conservancy, the Smithsonian Institution’s National Museum of the American Indian and the American Swedish Institute.
She gave away more than $200 million, and always anonymously.
She established the Anne Ray Charitable Trust which provides grants for charitable and educational programs and scholarships.
She provided that, after her death, the Margaret A. Cargill Foundation would use her wealth for charitable purposes. In 2011 her assets were finally liquidated, forming a $6 billion donation to the Anne Ray Charitable Trust and Margaret A Cargill Foundation.