City (pop., 2000: 122,377), capital of Kansas, U.S. Situated on the Kansas River, Topeka was founded in 1854 by a group of antislavery colonists and was prominent in the political conflict between proslavery groups and the antislavery Free Soil Party. In 1859 it was the headquarters for the building of the Atchison, Topeka, and Santa Fe Railway system. It has been the state capital since Kansas was admitted to the Union in 1861. The economy is based on agriculture, manufacturing, and governmental services. The Menninger family established its clinics there, making Topeka a national centre for the treatment of mental illness.