There are 5 US Post Offices in Wilson County serving a total of 8,934 residents equating to 1,787 residents per post office. It's estimated that approximately 14,260 packages are handled across the 5 county post offices annually. Wilson County (standard abbreviation: WL) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 9,409. Its county seat is Fredonia."