Sunset on Seattle and Mt. Rainer, Seattle, Washington. "Mount Rainier is the highest mountain of the Cascade Range of the Pacific Northwest, and the highest mountain in Washington. It is a large active stratovolcano located 59 miles south-southeast of Seattle, in Mount Rainier National Park. It is the most topographically prominent mountain in the contiguous United States and the Cascade Volcanic Arc, with a summit elevation of 14,411 feet. 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 produce massive lahars that could threaten the entire Puyallup River valley, and poses a grave threat to the southern sections of the 3.7-million-resident Seattle metropolitan area."