courtesy of the historychannel.com:
On this date (12/16) in 1881, 8.6 earthquake rocks the midwest:
In the Mississippi River Valley near New Madrid, Missouri, the greatest series of earthquakes in U.S. history begins when a quake of an estimated 8.6 magnitude on the Richter scale slams the region. Although the earthquake greatly altered the topography of the region, the area was only sparsely inhabited at the time, and there were no known human fatalities.
The earthquake raised and lowered parts of the Mississippi Valley by as much as 15 feet and changed the course of the Mississippi River. At one point, the Mississippi momentarily reversed its direction, giving rise to Reelfoot Lake in northwest Tennessee. A 30,000-square-mile area was affected, and tremors were felt as far away as the eastern coast of the United States, where the shock was reported to have rung church bells. Additional earthquakes and aftershocks continued throughout the winter and into the spring, and of the approximately 2,000 seismic vibrations felt during the period, five were estimated to be at an 8.0 or greater magnitude.
The New Madrid Fault system extends 120 miles southward from the area of Charleston, Missouri, to Marked Tree, Arkansas, and crosses through five states--Missouri, Illinois, Kentucky, Tennessee, and Arkansas. An earthquake of about 6.0 magnitude or greater occurs about every 80 years, and the catastrophic upheavals of the type reported in the winter of 1811 to 1812 occur about every 500 or 600 years.
This was just a bit downriver from us. The alarmists have suggested the ruin of St. Louis area next time New Madrid shifts.... Oh, and btw, it's pronounced New MAD-drid out here in the flatlands.