There are 3 US Post Offices in Clark County serving a total of 2,301 residents equating to 767 residents per post office. It's estimated that approximately 3,673 packages are handled across the 3 county post offices annually. Clark County (county code CA) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 2,215. Its county seat and most populous city is Ashland."