There are 1 US Post Offices in Arthur County serving a total of 400 residents equating to 400 residents per post office. It's estimated that approximately 638 packages are handled across the 1 county post offices annually. Arthur County is a county in the U.S. state of Nebraska. As of the 2010 census, the population was 460, making it Nebraska's least populous county and the fifth-least populous county in the United States (behind only Loving County, Texas, Kalawao County, Hawaii, King County, Texas, and Kenedy County, Texas). Its county seat and only incorporated community is Arthur. In the Nebraska license plate system, Arthur County is represented by the prefix 91 (it had the ninety-first-largest number of vehicles registered in the county when the license plate system was established in 1922). Arthur County contains the historic First Arthur County Courthouse and Jail, believed to be the smallest courthouse in the United States."