There are 5 US Post Offices in Johnson County serving a total of 5,304 residents equating to 1,061 residents per post office. It's estimated that approximately 8,466 packages are handled across the 5 county post offices annually. Johnson County is a county located in the U.S. state of Nebraska. As of the 2010 census, the population was 5,217. Its county seat is Tecumseh. The county was formed in 1855 and later organized in 1857. It was named after Vice President Richard M. Johnson. In the Nebraska license plate system, Johnson County is represented by the prefix 57 (it had the fifty-seventh-largest number of vehicles registered in the county when the license plate system was established in 1922)."