Fortune, with an eye towards American history, set out to uncover who the richest Americans of all time were. Wealth, as they say, is relative and converting a dollar amount to reflect the value of today's dollar isn't the most precise way to estimate worth, given that there are more people and far more dollars out there these days. Instead, the wealth of these ten men 9(yes, all men) was measured as a fraction of US gross domestic product (GDP) at the time of their death (or the most recent year, if not deceased). The top five are:

• John D. Rockefeller: Wealth at death: $1,400,000,000; 1/65 GDP
• Cornelius Vanderbilt: Wealth at death: $105,000,000; 1/87 GDP
• John Jacob Astor: Wealth at death: $20,000,000; 1/107 GDP
• Stephen Girard: Wealth at death: $7,500,000; 1/150 GDP
• Bill Gates: Wealth in 2006: $82,000,000,000; 1/152 GDP