In the past three centuries, major earthquakes outside of California and Alaska generally occurred in sparsely-settled areas, and damage and fatalities were largely minimal. But some took place in areas that have since been heavily built up. Among them are three earthquakes that occurred in 1811 and 1812 near New Madrid, MO. They are among the Great earthquakes of known history, affecting the topography more than any other earthquake on the North American continent. Judging from their effects, they were of a magnitude of 8.0 or higher on the Richter Scale. They were felt over the entire United States outside of the Pacific coast. Large areas sank into the earth, new lakes were formed, the course of the Mississippi River was changed, and forests were destroyed over an area of 150,000 acres. Many houses at New Madrid were thrown down. "Houses, gardens, and fields were swallowed up" one source notes. But fatalities and damage were low, because the area was sparsely settled then.