Since the first US bank notes were printed in 1861 to raise funds for the Civil War, they've been graced by the faces of presidents. The early days of paper money saw a variety of now-defunct notes, including silver certificates, Federal Reserve Bank Notes, interest bearing notes, and fractional currency - notes issued in lieu of coins during the Civil War. Almost all of these had an American president on them, though they weren't always consistent from printing to printing.
Despite the many different types of currency the US has issued, the main type of paper currency has always been consistent. These bills, and the coins that go with them, usually feature presidents, though several bills of note do not. Larger, now-discontinued bills have also featured presidents. Every sitting president either has or will be featured on presidential $1 coins, though these coins aren't being printed for circulation, only for collection.
This list of presidents on money includes all the presidents that have been featured on US currency, along with several prominent Americans who grace the nation's current bills but never held the highest office.
Jefferson has appeared on the $2 bill since its inception as a United States Note in 1862. It ceased printing briefly in 1966, but returned 10 years later and is still printed today.