Arapaho Glacier, Alpine glacier near North Arapaho Peak in Roosevelt National Forest, Colorado.

Arapaho Glacier is an alpine glacier in a cirque immediately southeast of North Arapaho Peak, in Roosevelt National Forest, Colorado. It lies just east of the Continental Divide and is the largest glacier in the state. It has lost over 52% of its surface area during the 20th century.

The glacier formed thousands of years ago during colder climate periods and was once far larger. Over the past hundred years it has shrunk significantly, reflecting how mountain climate patterns keep shifting.

Arapaho Glacier is the largest glacier in Colorado, and its meltwater helps supply the city of Boulder. The glacier sits in a cirque in Roosevelt National Forest, just east of the Continental Divide and southeast of North Arapaho Peak, so the water it releases feeds streams that serve communities far below.

The glacier sits in a cirque southeast of North Arapaho Peak, just east of the Continental Divide, in Roosevelt National Forest. The Arapaho Glacier Trail is the usual approach, a long climb with steep stretches and open rock; start early, wear sturdy boots and plan for sudden weather at high elevation.

Arapaho Glacier is the largest glacier in Colorado, yet it lost over 52% of its surface area during the 20th century and has a negative mass balance. Its meltwater helps supply the city of Boulder, Colorado.