Once, the United States issued $5,000, $10,000, and even $100,000 bills. Why on earth would someone carry bills that big, especially back when they were really worth something?
Believe it or not, it wasn’t just to save space in fatcats’ wallets. When the Treasury started printing these giant bills, their main purpose was making transfer payments between banks and other financial institutions. Before sophisticated wire transfer systems were fully developed, it was apparently easier and safer just to fork over a $5,000 bill to settle up with a fellow bank. Once transfer technology became safer and more secure, there really wasn’t much need for the big bills anymore.
Mental_floss has the story on when and why such large bills were issued, what they looked like, and why they aren't in circulation anymore. Link