Pauline Macmillan Keinath, Missouri
Keinath has $6.9 billion thanks to her shares in Cargill, the biggest private company in America. She happens to be the largest shareholder in the entire firm, which was started by her great-grandfather in 1865. The family still owns roughly 90% of the company.
Dennis Washington, Montana
Washington has made $6.2 billion in the construction industry. He used to work on the job sites, but now he owns a diversified business group called Washington Companies. He has stakes in copper mines, diamond mines, and regional railroads.