There are 9 US Post Offices in Hamilton County serving a total of 15,400 residents equating to 1,711 residents per post office. It's estimated that approximately 24,580 packages are handled across the 9 county post offices annually. Hamilton County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 15,673. The county seat is Webster City. The county was named in honor of William W. Hamilton, who served as President of the Iowa State Senate."