The unusual seismic activity began at about 2 a.m. on December 16, 1811, when a strong tremor rocked the New Madrid region. The city of New Madrid, located near the Mississippi River in present-day Arkansas, had about 1,000 residents at the time, mostly farmers, hunters and fur trappers. At 7:15 a.m., an even more powerful quake erupted, now estimated to have had a magnitude of 8.6. This tremor literally knocked people off their feet and many people experienced nausea from the extensive rolling of the earth. Given that the area was sparsely populated and there weren’t many multi-story structures, the death toll was relatively low. However, the quake did cause landslides that destroyed several communities, including Little Prairie, Missouri.

The earthquake also caused fissures–some as much as several hundred feet long–to open on the earth’s surface. Large trees were snapped in two. Sulfur leaked out from underground pockets and river banks vanished, flooding thousands of acres of forests. On January 23, 1812, an estimated 8.4-magnitude quake struck in nearly the same location, causing disastrous effects. Reportedly, the president’s wife, Dolley Madison, was awoken by the tremor in Washington, D.C. Fortunately, the death toll was smaller, as most of the survivors of the first earthquake were now living in tents, in which they could not be crushed.

The strongest of the tremors followed on February 7. This one was estimated at an amazing 8.8-magnitude and was probably one of the strongest quakes in human history. Church bells rang in Boston, thousands of miles away, from the shaking. Brick walls were toppled in Cincinnati. In the Mississippi River, water turned brown and whirlpools developed suddenly from the depressions created in the riverbed. Waterfalls were created in an instant; in one report, 30 boats were helplessly thrown over falls, killing the people on board. Many of the small islands in the middle of the river, often used as bases by river pirates, permanently disappeared. Large lakes, such as Reelfoot Lake in Tennessee and Big Lake at the Arkansas-Missouri border, were created by the earthquake as river water poured into new depressions.

This series of large earthquakes ended in March, although there were aftershocks for a few more years. In all, it is believed that approximately 1,000 people died because of the earthquakes, though an accurate count is difficult to determine because of a lack of an accurate record of the Native American population in the area at the time.

from:    http://www.history.com/this-day-in-history/earthquake-causes-fluvial-tsunami-in-mississippi