15. Mark Zuckerberg (1984-present)
> 2018 estimated net worth: $77.7 billion
> Source of wealth: Facebook
> Birthplace: White Plains, New York
Mark Zuckerberg’s rise to prominence is well known. While at Harvard, he created the social media juggernaut Facebook. Despite the company’s recent problems with the security of its data, Facebook still sports a steep valuation, and Zuckerberg is the nation’s wealthiest person under 40.
14. Jay Gould (1836-1892)
> 2018 estimated net worth: $78.3 billion
> Source of wealth: Railroads
> Birthplace: Roxbury, New York
Many 19th-century industrialists were notorious for their unscrupulous business practices and derisively called robber barons. Jay Gould may have been one of the most despised of this set because of his business practices. He reportedly issued fraudulent stock to buyers and bribed legislators to ensure that the sales went through. He rolled much of his profit into purchasing part of the Union Pacific Railroad.
13. Friedrich Weyerhaeuser (1834-1914)
> 2018 estimated net worth: $91.2 billion
> Source of wealth: Lumber
> Birthplace: Saulheim, Germany
Friedrich Weyerhaeuser left Germany at age 18 and began working at a sawmill in Illinois. After the economic downturn of 1857, Weyerhaeuser bought the mill and expanded his empire. He purchased logging operations around the Mississippi River. In 1900 he set a record for engaging in the largest private land transaction, when he bought 900,000 acres in Washington.
12. Warren Buffett (1930-present)
> 2018 estimated net worth: $92.1 billion
> Source of wealth: Berkshire Hathaway
> Birthplace: Omaha, Nebraska
Known as the “Oracle of Omaha,” Warren Buffett is a modern-day legend of investing and business diversification. He created his company, Buffett Partnership, in 1956 and quickly became a millionaire. He then purchased a textile company called Berkshire Hathaway but ended its textile division and purchased varied assets. Shares of Berkshire Hathaway are now among the most coveted stocks on the market. Buffett is also known for generous donations to charity; he has given away more than $32 billion.
11. Bill Gates (1955-present)
> 2018 estimated net worth: $92.2 billion
> Source of wealth: Microsoft
> Birthplace: Seattle, Washington
After founding Microsoft, Bill Gates ranked as the wealthiest person in America for more than 20 years. He famously dropped out of Harvard to create Microsoft with partner, Paul Allen. The company transitioned from making computing machines to also offering software. Today Investopedia ranks it as the world’s largest software company by revenue.