There are 6 US Post Offices in Cass County serving a total of 40,964 residents equating to 6,827 residents per post office. It's estimated that approximately 65,383 packages are handled across the 6 county post offices annually. Cass County is a county in the U.S. state of Michigan. As of the 2010 census, the population was 52,293. Its county seat is Cassopolis. Cass County is included in the South Bend\u2013Mishawaka, IN-MI, Metropolitan Statistical Area which has a total population of 316,663 and is sometimes considered part of Greater Michiana. Cass County has numerous lakes and is popular for fishing and boating."