Mount Jackson is a prominent peak in Glacier National Park’s Lewis Range, rising on the Continental Divide as the park’s fourth-tallest mountain. Highly visible from the Going-to-the-Sun Road, it is closely associated with Jackson Glacier and, on its southern flank, Harrison Glacier, the park’s largest remaining glacier. The mountain is an important part of Glacier’s alpine and glacial scenery. Its sedimentary rock was laid down in shallow seas from the Precambrian to the Jurassic periods, and its present form reflects the Lewis Overthrust, which began about 170 million years ago. Mount Jackson also has a severe alpine climate, with long, very cold winters and short summers.