There are 9 US Post Offices in Buchanan County serving a total of 17,920 residents equating to 1,991 residents per post office. It's estimated that approximately 28,602 packages are handled across the 9 county post offices annually. Buchanan County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 20,958. Its county seat is Independence. The county was created in 1837 and was named in honor of Senator James Buchanan, the 15th President of the United States."