There are 10 US Post Offices in Lake County serving a total of 33,647 residents equating to 3,365 residents per post office. It's estimated that approximately 53,704 packages are handled across the 10 county post offices annually. Lake County is a county located in the U.S. state of Montana. As of the 2010 census, the population was 28,746. Its county seat is Polson."