Greenup was initially planned in 1803 by Robert Johnson, a pioneer and legislator who owned the land. It was incorporated February 4, 1818, as Greenupsburg, named after Kentucky's third governor, Christopher Greenup. The name was shortened to Greenup in March 1872 to avoid confusion with Greensburg, Kentucky. Its post office was established on July 1, 1811, with Joshua Barlett as postmaster. Greenup is a city in Greenup County, Kentucky, at the confluence of the Ohio and Little Sandy Rivers. The population was 1,198 at the 2000 census. It is the county seat of Greenup County. Greenup is named in honor of Christopher Greenup.