Osage County is a county located in the U.S. state of Kansas. Its county seat is Lyndon, and its most populous city is Osage City. As of the 2020 census, the county population was 15,766. The county was originally organized in 1855 as Weller County, then renamed in 1859 after the Osage tribe.

Topeka is the capital city of the U.S. state of Kansas and the seat of Shawnee County. It is along the Kansas River in the central part of Shawnee County, in northeast Kansas, in the Central United States. As of the 2020 census, the population of the city was 126,587. The Topeka metropolitan statistical area, which includes Shawnee, Jackson, Jefferson, Osage, and Wabaunsee Counties, had a population of 233,870 in the 2010 census.