Udall is a city in Cowley County, Kansas, United States. As of the 2020 census, the population of the city was 661. The first post office at Ud…Udall is a city in Cowley County, Kansas, United States. As of the 2020 census, the population of the city was 661. The first post office at Udall was established in September 1879. J.M. Napier and P.W. Smith purchased a ten-acre tract from I.N Nelson in 1879. Udall was laid out in 1881 by Napier and Smith. It was named after English author Cornelius Udall. D.C. Green built the first house in Udall and opened a store.