9-1-1 is the emergency telephone number for the North American Numbering Plan (NANP), one of eight N11 codes. The use of this number is for emergency circumstances only, and to use it for any other purpose (including non-emergency situations and prank calls) can be a crime.
Read more about 9-1-1: History, Locating Callers Automatically, Funding 9-1-1 Services, Making Calls Public, GPS Locator