Kimberly Powell, blogging at About.com, lists the ten deadliest US disasters
(and the most lethal is not the most famous -- sorry, Galveston), with
some great related resources on each. Less systematic but also worth
checking out is the aggregator site Gen Disasters: Events That Touched Our Ancestors' Lives. Even though its home page appears to have gone away, you can browse by state or by disaster type.
Photo credit: http://www.flickr.com/photos/dedhed1950/8136458074/, from dedhed1950's photostream per Creative Commons
Harold Henderson, "Disasters Are Part of Genealogy, Too," Midwestern Microhistory: A Genealogy Blog, posted 1 November 2012 (http://midwesternmicrohistory.blogspot.com : accessed [access date]). [Please feel free to link to the specific post if you prefer.]