There are 5 US Post Offices in Gray County serving a total of 6,634 residents equating to 1,327 residents per post office. It's estimated that approximately 10,589 packages are handled across the 5 county post offices annually. Gray County (county code GY) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 6,006. Its county seat and most populous city is Cimarron."