The 1811-1812 New Madrid earthquakes were a series of intense seismic events that struck the New Madrid region along the Mississippi River between December 1811 and February 1812. These earthquakes are remembered for their extraordinary effects, including ground undulations and the temporary reversed flow of the Mississippi River. Despite their power and landscape-altering impacts, the quakes went largely unrecorded due to the region's sparse population. Recognized now as among the most powerful earthquakes in continental U.S. history, they left a lasting sense of mystery and awe.