There are 8 US Post Offices in Park County serving a total of 27,462 residents equating to 3,433 residents per post office. It's estimated that approximately 43,832 packages are handled across the 8 county post offices annually. Park County is a county located in the U.S. state of Montana. At the 2010 census, the population was 15,636. Its county seat is Livingston. A small part of Yellowstone National Park is located in the extreme southern part of the county."