There are 3 US Post Offices in Griggs County serving a total of 2,166 residents equating to 722 residents per post office. It's estimated that approximately 3,457 packages are handled across the 3 county post offices annually. Griggs County is a county located in the U.S. state of North Dakota. As of the 2010 census, the population was 2,420. Its county seat is Cooperstown. The county was founded in 1881 and later organized in 1882. It was named for Alexander Griggs."