Passed by Congress: 25 September 1789
Ratified: 15 December 1791
In Suits at common law, where the value in controversy shall exceed twenty dollars, the right of trial by jury shall be preserved, and no fact tried by a jury, shall be otherwise re-examined in any Court of the United States, than according to the rules of the common law.
Civil cases (that is, non-criminal cases involving a dispute between private parties) heard in federal courts are guaranteed trial by jury if the amount of money in dispute is greater than $20. We're guessing that $20 went a lot farther in 1790 than it does today…