If I recall my earthquake history right, the Mississippi River didn't flow backward until the February 1812 earthquake (about 8.8). It was a direct hit on New Madrid, and where the rapids were just SOUTH of town (UPSTREAM for those of you not already confused), (check your maps), that was the area that actually ROSE up when the earth gave way. There is a huge bend on the Illinois side of the river that points right at New Madrid. That bend is the northernmost edge of the plate that was jammed upward during the last big quake. That upward rising caused the Mississippi to roll backwards for a couple of hours. There are eyewitness accounts of this and you can read about it in a great book called "The Earthquakes American Forgot" by David Stewart and Ray Knox. Old New Madrid is located about 1/2 way between the Illinois riverbank and New Madrid today. Creepy, eh? You can find it at Amazon, Half.com, and for the horribly cheap (like me), at any library in Missouri. EXCELLENT book - I highly rec it for anyone who has even the slightest earthquake jones, like me. Oh, and at my website on the New Madrid page, there is a satellite image of the NMSZ, and you can see just how big the floodplain for the Mississippi/Ohio river really is. Lisa Farrand Kemp (The EarthQuack) http://pookie-baby.tripod.com/Farrand2000/index.html