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Warren Buffett is rich, but he's far from the richest person in history. As you can see in the chart above, his $61.2 billion net worth ranks him behind all 10 of the greatest American fortunes, accumulated by the likes of John D. Rockefeller, Cornelius Vanderbilt, and John Jacob Astor.

Buffett's wealth comes primarily from his interest in Berkshire Hathaway (NYSE:BRK-A) (NYSE:BRK-B), a sprawling conglomerate with a current market value of $319 billion. The 85-year-old Oracle of Omaha has been a director and the controlling shareholder of Omaha-based business since 1965 and its chairman and chief executive officer since 1970.

Berkshire Hathaway's latest proxy statement shows that Buffett controls 33.9% of the voting interest in the company and 19.6% of its economic interest. This is despite the fact that he's already transferred 185 million class B shares to the Bill & Melinda Gates Foundation, as a part of Buffett and Gates' Giving Pledge, a commitment by the world's wealthiest individuals and families to dedicate the majority of their wealth to philanthropy.

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Warren Buffett. Source: Thinkstock.

Based on his holdings of Berkshire Hathaway stock at the end of the first quarter -- which seems to slightly overstate his current net worth due presumably to his ongoing donations to the Gates Foundation -- Buffett's stake in Berkshire is worth $62.4 billion. This is split between his 38.4% interest in the company's class A shares, which trade for $193,705 per share and carry the greatest weight when it comes to voting, and his ownership of 261 million class B shares, which trade for a more affordable $128 per share.

Although Berkshire Hathaway was a largely washed-up textile company, it caught Buffett's eye. In the mid-1960s, the multibillionaire used its cash flows to expand into other industries as well as to fund a now $111 billion stock portfolio invested in the likes of Wells Fargo, American Express, and Coca-Cola. The chart below gives a sense for why Buffett's investment in Berkshire Hathaway has allowed him to climb the ranks of the richest people in American history. Namely, the company's book value per share has increased by 751,113%, based on data in Buffett's 2014 letter to shareholders.

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Interestingly, Buffett would be among the 10 richest people in American history if he hadn't already donated $23.7 billion worth of Berkshire Hathaway's class B shares. If you add those back in, he'd be worth roughly $85 billion, placing him ahead of the infamous railroad magnate from the Gilded Age, Jay Gould, who was worth an estimated $78.3 billion. Needless to say, this selflessness goes a long way toward explaining why Buffett is one of the most respected and revered financiers to ever live.

John Maxfield has no position in any stocks mentioned. The Motley Fool owns and recommends Berkshire Hathaway. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.