Net worth: $4 billion
Country: United States
Source of wealth: Medical devices – Cook Group
Overall Forbes rank: #329
In 2011, Ms. Cook inherited her late husband’s stake in the medical-device company they founded in a Bloomington, Ind., apartment building together in 1963. June 20th is Bill and Gayle Cook Day in Bloomington, on account of the couple’s extensive philanthropy work in the area.