January 23, 1812 —  Three earthquakes struck New Madrid, Missouri between 1811-1812, including one that hit today. They remain the most powerful earthquakes to hit the contiguous United States east of the Rocky Mountains in recorded history.

They were felt strongly over roughly 130,000 square kilometers (50,000 sq mi), and moderately across nearly 3 million square kilometers (1 million square miles).

The trio of earthquakes included: 

• December 16, 1811 — The epicenter in northeast Arkansas caused only slight damage to manmade structures, mainly because of the sparse population in the epicentral area.

• Today: January 23, 1812 — The epicenter was in the Missouri Bootheel. The meizoseismal area was characterized by general ground warping, ejections, fissuring, severe landslides, and caving of stream banks. Johnson and Schweig attributed this earthquake to a rupture on the New Madrid North Fault. This may have placed strain on the Reelfoot Fault.

• February 7, 1812 — The epicenter near New Madrid was destroyed. In St. Louis, many houses were severely damaged, and their chimneys were toppled. This shock was definitively attributed to the Reelfoot Fault by Johnston and Schweig. Uplift along a segment of this reverse fault created temporary waterfalls on the Mississippi at Kentucky Bend, created waves that propagated upstream, and caused the formation of Reelfoot Lake by obstructing streams in what is now Lake County, Tennessee.

Sources

• earthquake.usgs.gov
• wikipedia/NewMadridearthquakes
• U.S. Geological Survey: Largest Earthquakes in the United States