The idea for 911 first came about in 1957 when the National Association of Fire Chiefs wanted to establish a nationwide number for people to use to report fires. Over the next decade, various associations, recommendations and congressional debates determined that a single number for reporting all emergencies made more sense than having a different number for each type of emergency. It would be too hard to remember in an instant and so would defeat the purpose. The system’s creators choose “9-1-1” for a few of reasons: It’s short; it’s easy to remember; and it was not yet assigned as an area code or any other telephone-related number.

Haleyville, Alabama set up the first 9-1-1 system in the country in 1968.
Julia Layton. “How 9-1-1 Works”. July 12, 2006 http://people.howstuffworks.com/9-1-1.htm (March 13, 2007)