20. Larry Page (1973-present)
> 2018 estimated net worth: $55.7 billion
> Source of wealth: Google
> Birthplace: East Lansing, Michigan
Larry Page is the son of a computer scientist and a computer programming teacher. He and Sergey Brin invented the search engine Google while studying at Stanford University. Recently Page has been now personally funding a self-piloted flying taxi company, Kitty Hawk.
19. Larry Ellison (1944-present)
> 2018 estimated net worth: $57.8 billion
> Source of wealth: Oracle
> Birthplace: New York City, New York
Larry Ellison founded Oracle software company in 1977. The company got its big break in 1981 when IBM opted to use Oracle’s database management system. Oracle is now the second largest software company in the world, ranked by revenue, according to Investopedia.
18. Andrew Mellon (1855-1937)
> 2018 estimated net worth: $63.2 billion
> Source of wealth: Banking
> Birthplace: Pittsburgh, Pennsylvania
The son of wealthy banker Thomas Mellon, Andrew Mellon eventually took over his bank. The younger Mellon proved he had a keen eye for recognizing emerging technologies. He helped found the Aluminum Company of America and the Gulf Oil Corporation. He later served as a U.S. secretary of the Treasury for more than a decade.
17. Henry Ford (1863-1947)
> 2018 estimated net worth: $67.2 billion
> Source of wealth: Automobiles
> Birthplace: Dearborn, Michigan
Henry Ford became one of America’s most famous entrepreneurs due to the dominance of the Ford Motor Company. Ford was able to make cars efficiently and inexpensively after inventing the moving assembly line. By 1918, nearly half of all cars on American roads were Fords.
16. Marshall Field (1834-1906)
> 2018 estimated net worth: $75.0 billion
> Source of wealth: Department stores
> Birthplace: Conway, Massachusetts
A hardworking salesman, Marshall Field earned a fortune from his eponymous chain of department stores. He started a job at a Chicago mercantile house as a teen and worked his way up the store ranks to become a partner of the firm. He eventually bought out his partners and renamed his enterprise’s stores Marshall Field and Company.