There are 6 US Post Offices in Chickasaw County serving a total of 12,558 residents equating to 2,093 residents per post office. It's estimated that approximately 20,044 packages are handled across the 6 county post offices annually. Chickasaw County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 12,439. Its county seat is New Hampton. The county was named for the southern Indian Nation whose chief was Bradford."