There are 11 US Post Offices in Ionia County serving a total of 63,167 residents equating to 5,742 residents per post office. It's estimated that approximately 100,822 packages are handled across the 11 county post offices annually. Ionia County is a county located in the U.S. state of Michigan. As of the 2010 census, the population was 63,905. The county seat is Ionia. The Ionia County Courthouse was built by Claire Allen, a prominent southern Michigan architect. Ionia County comprises the Ionia, MI Micropolitan Statistical Area, which is also included in the Grand Rapids-Wyoming-Muskegon, MI Combined Statistical Area."