There are 1 US Post Offices in Grant County serving a total of 7,878 residents equating to 7,878 residents per post office. It's estimated that approximately 12,574 packages are handled across the 1 county post offices annually. Grant County (county code GT) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 7,829. Its county seat and only city is Ulysses."