Collier Glacier lies on the west slopes of North Sister in Oregon’s Cascade Range, generally above 8,000 feet in a high volcanic landscape shaped by snow, ice, and old lava. North Sister is an extinct shield volcano. The glacier is especially significant for the extent of its shrinkage since its last maximum during the Little Ice Age, dated here from about 1350 to 1850 A.D. Since that time, it has retreated by more than a mile, making it a clear example of long-term glacier change in the central Oregon Cascades.