There are 7 US Post Offices in Holt County serving a total of 10,186 residents equating to 1,455 residents per post office. It's estimated that approximately 16,258 packages are handled across the 7 county post offices annually. Holt County is a county in the U.S. state of Nebraska. As of the 2010 census, the population was 10,435. Its county seat is O'Neill. Holt County is in the Outback area of Nebraska. In the Nebraska license plate system, Holt County is represented by the prefix 36 (it had the 36th-largest number of vehicles registered in the county when the license plate system was established in 1922)."