Grand Lake was formed by glacial action as ice gouged back into the mountains to the east. As the climate warmed, the glacier melted irregularly, leaving ridges of clay and rocks called moraines. Moraines edge the west and north shore, and are also found within the lake and farther back into town. Since the area's early use as a summer ground by Native Americans, Grand Lake has been a tourist destination, enjoyed for its stunning beauty, recreational potential, and casual, therapeutic ambience.