Carbon Glacier on Mount Rainier’s north slope is the source of the Carbon River and has the lowest-elevation snout of any glacier in the contiguous United States, ending near 3,500 feet above sea level at its terminal moraine. It is also among the lower 48’s most massive glaciers, stretching about 5.7 miles, reaching around 700 feet thick, and holding roughly 0.2 cubic miles of ice—the greatest length, thickness, and volume of any U.S. glacier outside Alaska. Its cirque, more than a mile wide and backed by Willis Wall, is the largest in the Cascade Mountains.