Area code 406 is the sole area code for the entire state of Montana, making it one of the most iconic and easily recognizable area codes in the United States. Established in 1947, it has never been split or overlaid, serving all cities including Billings, Missoula, Bozeman, Helena, and Great Falls. The 406 area code represents Montana’s vast landscapes, low population density, and strong state identity. It’s widely used in branding for local businesses, tourism, and cultural events, symbolizing the rugged independence and natural beauty of Big Sky Country. 406 remains a source of pride for Montanans and a standout among area codes for its uniqueness and statewide reach.