GreenbackGreenback is a popular name for United States notes, a kind of paper money. The United States government first issued paper currency in 1861 to finance its Civil War operations. The first bills were redeemable in coins. But after 1862, the notes were only promises by the United States to pay. The reverse side of the bills was printed in green. Because the notes had no metal money behind them as security, people said they were backed only by green ink. In time, the notes became known as greenbacks. At one time when people held little confidence in the government, greenbacks were worth only 35 cents in coin for each dollar.