1811-1812 (*cough*).
The interesting thing about the New Madrid quake is that is often given as a period of time rather than as a specific point in time. There were many violent earthquakes during this period, not just one. When you consider that the geological explanation for that event was the North American continent ripping itself into two pieces, it seems more reasonable.
There were 3 main events for the 1811-1812 sequence, all now regarded as Moment magnitude 7 to 8....and of course many 5-6 range aftershocks interspersed within them.
The North American continent wasn't and isn't ripping apart. The earthquakes occured on a a very old "failed" rift wher the continent began to split and stopped. The general stress of the movement of North America westwards does build up in the rift and cause the quakes, but the continent is not separating in the NMSZ and isn't going to.