Mount St Helens

Mount St Helens in an  active volcano in Washington  state  

most famous for its major eruption May 18, 1980, the deadliest and most economically destructive volcanic event in U.S. history.  Fifty-seven people were killed; 200 homes, 47 bridges, 15 miles (24 km) of railways, and 185 miles (298 km) of highway were destroyed. A massive debris avalanche, triggered by an earthquake of magnitude 5.1, caused a lateral eruption that reduced the elevation of the mountain's summit from 9,677 ft (2,950 m) to 8,363 ft (2,549 m), leaving a 1 mile (1.6 km) wide horseshoe-shaped crater. The debris avalanche was 0.6 cubic miles (2.5 km3) in volume.  Ever since its main eruption, it had continuous volcanic activity until 2008. Despite this, geologists predict that future eruptions will be more destructive, since the configuration of the lava domes there require more pressure to erupt.  

 It was deemed a National Monument in 1982 by President Ronald Reagan

•  Source: Wikipedia