Located only 12 miles from Juneau, Alaska, Mendenhall Glacier extends about 13 miles from the Juneau Icefield to the Mendenhall River. It is part of the federally protected Tongass National Forest. The glacier was formed by accumulating snowfall over thousands of years. As new snow fell over old snow, the old snow became compacted into solid ice.

The Mendenhall Glacier is one of 38 glaciers that make up the Juneau Icefield, North America's fifth largest icefield. Like many glaciers, the Mendenhall is retreating. Since 1700, it has retreated 2.5 miles. Mendenhall's retreat has resulted in the formation of Lake Mendenhall, which was first documented in 1931.