It seems that the U.S. disasters that took the most lives happened the furthest back in time and from natural causes. The largest loss of life occurred in 1900 when a hurricane wiped out Galveston Island, Texas. It claimed 6000 to 12,000 lives. Since there were so many lost or missing, an accurate account could never be determined, but even the low number is still the highest loss of life that I could find and only shared that position with the 1906 earthquake and fire in San Francisco where 3,000 to 6,000 casualties happened.
The next, or 3rd most deadly disaster was also a hurricane that killed 3,000+ and caused huge amounts of damage. The 4th disaster in loss of life was man made. It was caused by terrorism when the hijacked airliners hit the twin towers in New York City and the Pentagon in D.C. That caused over a billion dollars in damage, which is just a drop in the bucket compared to 108 billion that Hurricane Katrina caused, which was (so far) the costliest natural disaster in the history of the U.S.
The weatherman is calling for more rain, just what this rain-soaked and flooded area needs. I guess those poor people who just got flooded out in Houston should hold off on the clean up. Now make sure you all stay far away from any disaster and have a great day, you hear?