A stratovolcano in the Cascades of Washington state. It is about 100 miles south of Seattle and about 50 miles north of Portland. It last erupted in May 1980, killing 57 people in the most devastating volcanic eruption in U.S. history. Perhaps the most famous casualty of that eruption was an innkeeper named Harry Truman (no relation to the president of the same name) who refused to evacuate from the mountain. Because of an avalanche of volcanic debris during that eruption, Mount Saint Helens lost about 1300 feet in height; lahars (mudflows of pyroclastic material) reached all the way to the Columbia River. The volcano is surrounded by Gifford Pinchot National Forest.