The richest Americans in history come primarily from several eras of extreme inequality.One group of robber barons, like John D. Rockefeller and Andrew Carnegie, lived between the Gilded Age and the Roaring Twenties.
Then there are the tech mavens and investors who made a fortune in the past 20 years.
We identified peak net worth for historical figures based on scholarly estimates. All figures are adjusted for inflation.
Peak fortune: $68.5
Source of wealth: Major of the US Militia and member of the New York State Assembly, Rensselaer was also heir to one of the most well-endowed estates in the US. He founded the Rensselaer Polytechnic Institute with a portion of his wealth.
Peak fortune: $71.2
Source of wealth: Railroad baron and gold speculator, Jay Gould masterminded the 19th century transportation boom in America. He and financier James Fisk also bought up a dominating share of the gold market at the time - enough to directly affect market movements during Gould's lifetime.
Peak fortune: $105 billion
Source of wealth: Successful in the shipping trade, he was a French-born American merchant who went into the banking business later in his life, owning a bank that was called 'Girard's Bank'.
Peak fortune: $121 billion
Source of wealth: A successful fur trader, he established a near monopoly within the U.S. by around 1800. He subsequently switched trades and went on to investing in real estate, focusing on New York City.
Peak fortune: $136 billion
Source of wealth: Founded Microsoft with Paul Allen in 1975. He held onto shares as Microsoft dominated the age of computers, peaking in personal wealth at the top of the Dot Com Bubble.
Estimate from wide-spread reports of a $101 billion net worth for a period in 1999, adjusted for inflation.
Fortune: $185 billion
Source of wealth: In 1862, he began to buy railroad lines. Although already 70 years old, his wealth mostly comes from this business of the 19th century. Prior to that, he was known as a cold-blooded steam-boat entrepreneur.
Fortune: $336 billion
Source of wealth: He founded Standard Oil in 1870, at the age of 31, and bought up most of the oil refineries in the United States, eventually controlling about 90% of the American oil business.
Business Insider Emails & Alerts
Site highlights each day to your inbox.