Missouri: December 16, 1811
The New Madrid fault -- near where Missouri, Kentucky, Arkansas, and Tennessee meet -- witnessed an 8.0 or greater magnitude quake nearly 200 years ago. The shaking spread so far that church bells reportedly rang in Boston, more than 1,500 miles away! It had dramatic effects on the area's geography, lifting up land enough to make the Mississippi River appear to flow upstream. Fortunately, the sparsely populated area suffered only one death and minimal property damage.
Related HowStuffWorks Articles
The fire under the tiny town of Centralia, Pennsylvania, has been burning since at least 1962 and, to this day, nobody knows how to put it out.