There are 3 US Post Offices in Liberty County serving a total of 2,035 residents equating to 678 residents per post office. It's estimated that approximately 3,248 packages are handled across the 3 county post offices annually. Liberty County is a county located in the U.S. state of Montana. As of the 2010 census, the population was 2,339. Its county seat is Chester. The county was established in 1919. Liberty County is home to Tiber Dam, which is located in the south western part of the county. It is south of the Canada\u2013US border with Alberta.