St. Mary Lake is the second largest lake in Glacier National Park, Montana. Located on the
east side of the park, the Going-to-the-Sun Road parallels the lake along its north shore.

The lake is 9.9 miles (15.9 km) long and three hundred feet (100 m) deep. The waters of the
lake rarely rise above 50°F (10°C) and is home to various species of trout. During the winter,
the lake often is frozen completely over with ice up to four feet (1 m) thick.