Mount St. Helens' Past Eruptions

Mount St. Helens is the youngest and most active of the Cascade volcanoes. While recent studies have found evidence of eruptive activity back 300,000 years, incredibly, most of the volcano we see today was erupted over the last 3,000 years.

MSH eruptive history (275,000 to 3,900 years ago):

http://volcanoes.usgs.gov/volcanoes/st_helens/st_helens_geo_hist_102.html

MSH eruptive history (3,900 years ago to 1980):

http://volcanoes.usgs.gov/volcanoes/st_helens/st_helens_geo_hist_108.html

Historical FAQs:

http://volcanoes.usgs.gov/volcanoes/st_helens/st_helens_sub_page_77.html