Ellsworth County (county code EW) is a county located in Central Kansas, in the Central United States. As of the 2010 census, the county population was 6,497. Its county seat and most populous city is Ellsworth.
For millennia, the land now known as Kansas was inhabited by Native Americans. In 1803, most of modern Kansas was secured by the United States as part of the Louisiana Purchase. In 1854, the Kansas Territory was organized, then in 1861 Kansas became the 34th U.S. state.
Ellsworth County was established February 26, 1867. The county was named after the old Fort Ellsworth, which was named in honor of 2nd Lieutenant Allen Ellsworth of the 7th Iowa Cavalry (Company H), who supervised construction of the fort in 1864. On November 17, 1866, the fort was renamed Fort Harker in honor of General Charles Garrison Harker who had died on June 27, 1864, from wounds received in an abortive offensive action in the Battle of Kennesaw Mountain. The fort was subsequently moved to a new site about one mile to the northeast, and the old fort's remaining buildings were ordered torn down in June 1867.