For those of you who share my interest in the history of disasters and emergency management in the U.S., I recommend this new journal article: US Presidents and Their Role in Emergency Management and Disaster Policy, 1950-2009, by Naim Kapucu, et al.
This 34 page article is available as a free download, once you login.
NOTE: As you will see from the comment made today by Bill Cumming, the authors did not get all of their dates and facts correct. Generally I defer to Bill on such matters.
Also, I am working on a second edition of the text Emergency Management; the American Experience, 1900-2010, due out in 2012. That book will contain carefully fact-checked details on the history of emergency management for the past 110 years.