The New Madrid Earthquake, one of the largest earthquakes ever recorded in the contiguous United States, occurred on February 7, 1812. It got its name from its primary location in the New Madrid Seismic Zone, near New Madrid, Louisiana Territory (now Missouri).
This earthquake was preceded by three other major quakes: two on December 16, 1811, and one on January 23, 1812. These earthquakes destroyed approximately half the town of New Madrid. There were also numerous aftershocks in the area for the rest of that winter.
There are estimates that the earthquakes were felt strongly over 50,000 square miles (130,000 km²), and moderately across nearly one million square miles. The historic San Francisco earthquake of 1906, by comparison, was felt moderately over 6,000 square miles (16,000 km²).
Based on the effects of these earthquakes, it can be estimated that they had a magnitude of 8.0 on the Richter scale. As a result of the quakes, large areas sank into the earth, new lakes were formed (notably Reelfoot Lake, Tennessee), and the Mississippi River changed its course, creating numerous geographic exclaves, including Kentucky Bend, along the state boundaries defined by the river.
Some sections of the Mississippi River appeared to run backward for a short time. Sandblows were common throughout the area, and their effects can still be seen from the air in cultivated fields. Church bells were reported to ring in Boston, Massachusetts and sidewalks were reported to have been cracked and broken in Washington, D.C.