Montana may not be as famous for earthquakes as its neighbors to the west, but it is one of the top 10 most seismically active states. The largest earthquake in recent history in Montana occurred in 1959. With a 7.5 magnitude, the Hebgen Lake Earthquake set off a landslide of 58 million cubic yards of earth that: dammed the Madison River, killed 28 people and created Quake Lake. Such large earthquakes are rare, but 7-10 small earthquakes occur every day in Montana.
Information on earthquake preparedness can be found through the following links.