Harrisonville is a city in Cass County, Missouri, United States. The population was 10,019 at the 2010 census. It is the county seat of Cass County.
Harrisonville was founded in 1837 upon 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 notorious General Order No. 11 (1863), which ordered the depopulation of three entire Missouri counties and part of a fourth.In 1972, Harrisonville was the site of escalating tensions between a handful of would-be hippies—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 motivation turned out to be personal, not political; he had saved money to buy a farm, but the seller had recently backed out of the deal, and Simpson had used the money to bail his friends out of jail.