There are 5 US Post Offices in Frontier County serving a total of 2,575 residents equating to 515 residents per post office. It's estimated that approximately 4,110 packages are handled across the 5 county post offices annually. Frontier County is a county in the U.S. state of Nebraska. As of the 2010 census, the population was 2,756. Its county seat is Stockville. In the Nebraska license plate system, Frontier County is represented by the prefix 60 (it had the sixtieth-largest number of vehicles registered in the county when the license plate system was established in 1922)."