There are 7 US Post Offices in Valley County serving a total of 6,897 residents equating to 985 residents per post office. It's estimated that approximately 11,008 packages are handled across the 7 county post offices annually. Valley County is a county located in the U.S. state of Montana. Valley County was created from the division of Dawson County in 1893. As of the 2010 census, the population was 7,369. Its county seat is Glasgow. It is located on the Canada\u2013United States border with Saskatchewan."