There are 7 US Post Offices in Cass County serving a total of 38,523 residents equating to 5,503 residents per post office. It's estimated that approximately 61,487 packages are handled across the 7 county post offices annually. Cass County is a county located in the U.S. state of Indiana. As of 2010, its population was 38,966. The county seat is Logansport. Cass County comprises the Logansport, IN Micropolitan Statistical Area.