There are 10 US Post Offices in Madison County serving a total of 6,424 residents equating to 642 residents per post office. It's estimated that approximately 10,253 packages are handled across the 10 county post offices annually. Madison County is a county located in the U.S. state of Montana. As of the 2010 census, the population was 7,691. Its county seat is Virginia City. The county was founded in 1865. At the time it was part of the Montana Territory."