The first anniversary of the deadly Joplin, Mo., tornado is May 22, 2012. Here's a look at the 10 deadliest tornadoes in U.S. history, according to the NOAA.
2. Natchez, Miss. (1840) -- An estimated 317 people died and 109 people were injured by this tornado, although the death toll was probably larger because slave deaths were likely not included.