Mount Rainier is the highest mountain of the Cascade Range of the Pacific Northwest, and the highest mountain in the U.S. state of Washington. It is a large active stratovolcano located 54 miles south-southeast of Seattle. It is the most topographically prominent mountain in the contiguous United States and the Cascade Volcanic Arc, with a summit elevation of 14,411 ft. Mt. Rainier is considered one of the most dangerous volcanoes in the world, and it is on the Decade Volcano list. Because of its large amount of glacial ice, Mt. Rainier could potentially produce massive lahars that could threaten the entire Puyallup River valley, and poses a grave threat to sections of Seattle, a city of over 650,000 people with more than 3.7 million living in its metropolitan area.