There are 6 US Post Offices in Harper County serving a total of 5,954 residents equating to 992 residents per post office. It's estimated that approximately 9,503 packages are handled across the 6 county post offices annually. Harper County (county code HP) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 6,034. Its county seat and most populous city is Anthony. The county was named for Sergeant Marion Harper of the 2nd Kansas Cavalry, who died of wounds suffered near Waldron, Arkansas, in December 1863."