New Madrid (măˈdrĭd) [key], city (2000 pop. 3,334), seat of New Madrid co., extreme SE Mo., on Mississippi River at the sweeping New Madrid Bend; inc. 1808. A river port, the city is protected by high levees; cotton, wood products, and telecommunications shelters are produced, and aluminum is processed. Laid out (1789) when under Spanish rule, the city has been moved several times as the Mississippi has shifted, and the original townsite is under the river. In the Civil War, Federal troops captured New Madrid before taking (1862) nearby Island No. 10 (now vanished).
The city has given its name to the New Madrid Fault System, which runs SW to NE from NE Arkansas and W Tennessee through SE Missouri and W Kentucky into S Illinois. Numerous earthquakes have occurred in this seismic zone, most notably the severe earthquakes of 1811 and 1812, a time when the region was still thinly populated. The three quakes reversed the flow of the Mississippi, created Reelfort Lake in Tennessee, rang church bells in Boston, and were felt in Canada and Charleston, S.C.
See studies by J. L. Penick (rev. ed., 1982), M. L. Fuller (4th ed., 1995), and J. Feldman (2006).