There are 3 US Post Offices in Clarke County serving a total of 8,773 residents equating to 2,924 residents per post office. It's estimated that approximately 14,003 packages are handled across the 3 county post offices annually. Clarke County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 9,286. The county seat is Osceola. The county was formed on January 13, 1846. It was named for James Clarke, a Governor of the Iowa Territory."