Jamestown is a city in Cloud County, Kansas, United States. As of the 2020 census, the population of the city was 237. Jamestown was fou…Jamestown is a city in Cloud County, Kansas, United States. As of the 2020 census, the population of the city was 237. Jamestown was founded in 1878, and was incorporated as a city in 1883. It was named for either Senator James Pomeroy, or James P. Pomeroy, a railroad official. A post office was opened in Alva in 1871, but it was moved to Jamestown in 1878. The town located itself on the Missouri Pacific Railroad.