Note from Joan Young via Rootsweb Review:
Sometimes the factors involved in ancestral deaths could indicate that family members died as the result of a disaster. Disasters should be considered when multiple family members died at exactly the same time. A disaster could be an earthquake, flood, fire, shipwreck, mining accident, train wreck, etc. (Previously published in RootsWeb Review: 12 November 2008, Vol. 11, No. 21)

Disaster listings at Cyndi's List

Disasters in the United States, 1650-2005

Disaster Database

The Nation's Top 10 Natural Disasters pre 1940

By The Associated Press

Hurricane Katrina's latest death toll makes it the nation's 10th deadliest, so far:
1. Galveston (Texas) Hurricane, 1900, estimated 8,000 deaths
2. Great Okeechobee Hurricane in Florida, 1928, estimated 2,500-plus
3. Johnstown, Pa., Flood, 1889, estimated 2,200-plus
4. Louisiana Hurricane, 1893, 2,000-plus
5. South Carolina-Georgia Hurricane, 1893, 1,000-2,000
6. Great New England Hurricane, 1938, 720
7. San Francisco Earthquake, 1906, 700
8. Georgia-South Carolina Hurricane, 1881, 700
9. Tri-State Tornado in Missouri, Illinois and Indiana, 1925, 695
10. Hurricane Katrina, with the latest toll at 659.

(Previously, the 10th deadliest disaster was the Labor Day Hurricane that hit the Florida Keys, 1935, 405). Source: Rusty Pfost, meteorologist with the National Weather Service and The Associated Press.