These people look rich, but they're not among the 10 richest Americans of all time. Source: iStock/Thinkstock.

Bill Gates and Warren Buffett are rich, but their fortunes don't come anywhere near those from earlier periods in American history. In fact, after adjusting for inflation, neither Gates nor Buffett even makes the list of the 10 richest Americans of all time. This is despite the fact that they're worth an estimated $78.8 billion and $61.2 billion, respectively.

Check out the slideshow below to learn 10 fascinating facts about the biggest fortunes in American history. You'll discover the railroad entrepreneur who made the list despite dying at the tender age of 56, the landholder who inherited his entire fortune, and how many members of this elite club weren't even born in the United States (hint: it's a substantial portion).