Mulvane is a city in Sedgwick and Sumner counties in the U.S. state of Kansas. As of the 2020 census, the population of the city was 6,286. …Mulvane is a city in Sedgwick and Sumner counties in the U.S. state of Kansas. As of the 2020 census, the population of the city was 6,286. Mulvane was laid out in 1879 at the junction of five Santa Fe rail lines. It is named for Joab R. Mulvane, a railroad official who was instrumental in bringing the Atchison, Topeka, and Santa Fe Railroad to Mulvane.