There are 10 US Post Offices in Hardin County serving a total of 16,650 residents equating to 1,665 residents per post office. It's estimated that approximately 26,575 packages are handled across the 10 county post offices annually. Hardin County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 17,534. The county seat is Eldora. The county was named in honor of Col. John J. Hardin, of Illinois, who was killed in the Mexican\u2013American War."