There are 3 US Post Offices in Grant County serving a total of 2,020 residents equating to 673 residents per post office. It's estimated that approximately 3,224 packages are handled across the 3 county post offices annually. Grant County is a county located in the U.S. state of North Dakota. As of the 2010 census, the population was 2,394. Its county seat is Carson. Until November 28, 1916, Grant County was a part of Morton County. The county was named in honor of General Ulysses S. Grant."