70. Pauline Macmillan Keinath
Believed to be the biggest individual shareholder in America’s largest privately held company, Macmillan Keinath owns an estimated 12% stake in $110 billion (sales) Cargill. Her great-grandfather W.W. Cargill founded Cargill in 1865. The son of a Scottish sea captain, Cargill started the business with a single grainstorage warehouse at the end of an Iowa railroad line. He got rich as railroads expanded west and opened up the frontier. His heirs still own roughly 90% of the company.