Harrisonville is a town in Cass County, Missouri, United States. The population was 10,121 at the 2020 census. It is the county chair of Cass
County. It is allocation of the Kansas City metropolitan area.

Harrisonville was founded in 1837 on land donated to Cass County by Congress for county purposes, and was named for Congressman Albert G. Harrison, who was instrumental in obtaining the land grant. The area suffered greatly during the American Civil War, though Harrisonville was one of the few places exempted in Union General Thomas Ewing’s General Order No. 11 (1863), which ordered the depopulation of three entire Missouri counties and portion of a fourth.

In 1972, Harrisonville was the site of escalating tensions in the company of a handful of mostly Vietnam veterans and town elders, which culminated in a brief rampage by 25-year-old Charlie “Ootney” Simpson. In the town square, in plain view of onlookers, he killed two police officers and a bystander before shooting himself. The victims were officers Donald Marler and Francis Wirt and local businessman Orville Allen. His aspiration turned out to be personal, not political; he had saved child support to buy a farm, but the seller had recently backed out of the deal, and Simpson had used the keep to bail his friends out of jail.

The Robert A. Brown House, Harrisonville Courthouse Square Historic District, and St. Peter’s Episcopal Church are listed upon the National Register of Historic Places.