There are 14 US Post Offices in Cascade County serving a total of 54,563 residents equating to 3,897 residents per post office. It's estimated that approximately 87,089 packages are handled across the 14 county post offices annually. Cascade County (cascade means waterfall in French) is a county located in the U.S. state of Montana. As of the 2010 census, the population was 81,327, making it the fifth-most populous county in Montana. Its county seat is Great Falls. Cascade County comprises the Great Falls, MT Metropolitan Statistical Area."