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The U.S. Geological Survey says the quake hit at 6:14 a.m. Monday with the epicenter about 32 miles west of West Yellowstone.
That would put the quake's location north of the Continental Divide, in the Centennial Valley.
The area is sparsely populated, and even an hour after the quake only a couple of people had reported feeling the quake to U.S.G.S.
The region on the west side of Yellowstone frequently has several small quakes per month, but Monday's quake was larger than usual.
According to the USGS, Montana is one of the most seismically-active states in the country, although the vast majority of recorded earthquakes are very small, causing no damage and rarely noticed by people.
Since 1925, the state has experienced five shocks that reached intensity VIII or greater (Modified Mercalli Scale). During the same interval hundreds of less severe tremors were felt within the State.
Montana's earthquake activity is concentrated mostly in the mountainous western third of the State which lies within a seismic zone that also includes southeastern Idaho, western Wyoming, and central Utah.
Additional information by David Sherman
of the continental divide.