Greenback was named for the nearby Greenback Mine, a gold and quartz mine which was once the richest mine in Oregon by feet of tunnel mined.[4] The Greenback Mine was established by Len Browning and Edward Hanum in 1897. It was sold to banker William Brevoot in 1902, and he founded the town.[5] The post office was established in August 1902 and disestablished in June 1908. Carey W. Thompson was the first postmaster.[6][7]