There are 11 US Post Offices in Cass County serving a total of 30,504 residents equating to 2,773 residents per post office. It's estimated that approximately 48,688 packages are handled across the 11 county post offices annually. Cass County is a county located in the U.S. state of Texas. As of the 2010 census, its population was 30,464. The county seat is Linden. The county was named for Lewis Cass, a senator from Michigan who favored the annexation of Texas."