Born poor in upstate New York, Sage started out as a grocery store clerk. But he was a prodigious worker, saver and trader, and soon had enough money for his own shop. From there, he expanded into horse brokering, shipping and making loans to friends.

Sage hit his stride in New York City, trading stocks and pioneering the system of puts and calls still used on Wall Street today. These gave Sage the ability to buy or sell stock at predetermined prices. He was a friend of Jay Gould (No. 10), and the two often teamed up to manipulate share prices.

Famously stingy (he was once caught stealing a cheap fan from the boardroom of Western Union), Sage's wife gave away most of his fortune after his death. One of the main organizations she founded -- the Russell Sage Foundation -- specifically works to improve living conditions in the United States.