Mount St. Helens erupts in Washington, United States, killing 57 people and causing $3 billion in damage.

Mount St. Helens is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It lies 52 miles (83 km) northeast of Portland, Oregon, and 98 miles (158 km) south of Seattle. Mount St. Helens takes its English name from that of the British diplomat Alleyne FitzHerbert, 1st Baron St Helens, a friend of explorer George Vancouver who surveyed the area in the late 18th century. The volcano is part of the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire.

In March 1980 a series of volcanic explosions and pyroclastic flows began at Mount St. Helens in Skamania County, Washington, United States. A series of phreatic blasts occurred from the summit and escalated for nearly two months until a major explosive eruption took place on May 18, 1980, at 8:32 a.m. The eruption, which had a volcanic explosivity index of 5, was the first to occur in the contiguous United States since the much smaller 1915 eruption of Lassen Peak in California. It has often been considered the most disastrous volcanic eruption in U.S. history.

Washington, officially the State of Washington, is a state in the Pacific Northwest region of the United States. It is often referred to as Washington State to distinguish it from the national capital, both named after George Washington. Washington borders the Pacific Ocean to the west, Oregon to the south, Idaho to the east, and shares an international border with the Canadian province of British Columbia to the north. Olympia is the state capital, and the most populous city is Seattle.