It was set up in 1968 in the United States, but was not applicable to the whole country until the early 1980s.
In over 99% of locations in the United States and Canada, dialing "911" from any telephone will link the caller to an emergency dispatch center which can send emergency responders to the caller's location in an emergency. In some areas enhanced 911 is available, which automatically gives dispatch the caller's location, if available.
When the 9-1-1 system was originally introduced, it was advertised as the "nine-eleven" service. This cause some problems when people looked for the "eleven" key on their telephones. Therefore, all references to the telephone number 9-1-1 are now always made as nine-one-one—never as nine-eleven (See September 11, 2001 attacks).
Dialing 911 from a mobile phone will reach the state police or highway patrol. The caller will have to describe his or her exact location so that the state police can transfer the call to the correct local emergency services. It is therefore more efficient to store into the mobile phone the direct phone number to the local police or other emergency services.
The number's close association with emergency situations has led to "911" being used as shorthand for "emergency" in text messages sent to pagers and mobile phones. Additionally, 911 is used so pervasively in US media that other countries have sometimes had difficulty in educating children not to dial 911 for help. For example, the UK number is 9-9-9, the European and GSM number is 1-1-2, the Australian number is 0-0-0, and the Japanese numbers are 1-1-0 for the police and 1-1-9 for other emergencies.
9-1-1 Emergency Telephone Number Day was proclaimed, by President Reagan in 1987, to occur on the 11th day of September, the ninth month, of that year. The proclamation was made to promote the North American universal emergency telephone number 9-1-1.
Since then has been celebrated by many United States communities as "9-1-1 emergency number day" or simply "911 day". The promotional effort is often lead by firefighters and the Police.9-1-1 Emergency Telephone Number Day