St. Mary is an unincorporated community on the western border of the Blackfeet Indian Reservation adjacent to Glacier National Park in Glacier County, Montana, United States. The village is the eastern terminus of the Going-to-the-Sun Road which bisects the park east to west, a distance of 53 mi (85 km). Fewer than 50 people reside in the village year-round; however, the population increases tenfold on a busy summer evening. Several lodges, restaurants and cafés, a small grocery store, two gas stations and campgrounds are located in the village. A large housing area for National Park Service personnel is located adjacent to the village, but within the park.
U.S. Route 89 passes through the village, which lies between Saint Mary Lake in Glacier National Park and Lower St. Mary Lake on the Blackfeet Indian Reservation.
This climatic region is typified by large seasonal temperature differences, with warm to hot (and often humid) summers and cold (sometimes severely cold) winters. According to the Köppen Climate Classification system, St. Mary has a humid continental climate, abbreviated "Dfb" on climate maps.
Coordinates: 48°44′37″N 113°25′42″W / 48.7436°N 113.4284°W