Final answer:
The large earthquakes in 1811-1812 struck near the town of New Madrid, Missouri, and are known as a series of strong seismic events that caused notable geographical alterations.
Step-by-step explanation:
The large earthquakes in question struck near the town of New Madrid, Missouri in 1811-1812. These seismic events are now known as the New Madrid earthquakes and were estimated to be in the magnitude range of 7.0 to 7.5 on the Richter scale.
The New Madrid earthquakes caused significant geographical changes, including rerouting parts of the Mississippi River, and were felt as far away as New York City and Washington D.C.