There are 2 US Post Offices in Cheyenne County serving a total of 2,691 residents equating to 1,346 residents per post office. It's estimated that approximately 4,295 packages are handled across the 2 county post offices annually. Cheyenne County (county code CN) is a county located in the northwest portion of the U.S. state of Kansas. Official website is www.cncoks.us. As of the 2010 census, the county population was 2,726. Its county seat and most populous city is St. Francis."