There are 4 US Post Offices in Mitchell County serving a total of 9,175 residents equating to 2,294 residents per post office. It's estimated that approximately 14,644 packages are handled across the 4 county post offices annually. Mitchell County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 10,776. The county seat is Osage. The county is named in honor of John Mitchel."