Greenup, the seat of Greenup county, was established in 1803 with the new county and named Greenupsburg, like the county for Christopher Greenup. It is located at the mouth of the Little Sandy River on the Ohio River. The name was shortened to Greenup in 1872. Adjacent to Greenup to the southeast was the town of Riverton, which is now within Greenup. The Greenup Court House post office opened in 1811 and was renamed Greenup in 1872. The population in 1990 was 1,158.