On April 2, 1862, the first greenback left the U.S. Treasury, marking the start of a new era in the American monetary system.
At the start of the Civil War, the U.S. didn't have a national paper currency. Instead, the money supply consisted of U.S. coins and a collection of paper notes issued by private banks. Technically, the federal government began issuing its own paper currency in 1861. That year, the Lincoln administration issued $60 million in demand notes, a variant of a Treasury note that was redeemable "on demand" for gold coins at the Treasury or any sub-Treasury.