Pinnacle Glacier is one of the named glaciers on the west slopes of Mount Adams in Washington’s Gifford Pinchot National Forest. High on the stratovolcano, it descends from about 10,000 feet to a terminus near 7,200 feet. Harry Fielding Reid named it in 1901 while surveying Mount Adams’ glaciers with C. E. Rusk. Over time, like many glaciers in the Cascades, it has changed significantly; between 1904 and 2006, it lost 7 percent of its surface area. It remains part of Mount Adams’ glaciated upper slopes.