911 (emergency call)

911 is dialed for emergency calls; 311 is for non-emergency calls. The 911 system was introduced in New York City -- and nationwide -- in 1968. In the 1967 phonebook, Fire was "OPERATOR" and Police and Ambulance were dialed with "440-1234."


Wikipedia: 9-1-1
9-1-1 is the emergency telephone number for the North American Numbering Plan (NANP), one of eight N11 codes. This number is intended for use in emergency circumstances only, and to use it for any other purpose (including non-emergency situations and prank calls) can be a crime.[

History
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The first known experiment with a national emergency telephone number occurred in the United Kingdom in 1937, using the number 999. The first city in North America to use a central emergency number (in 1959) was the Canadian city of Winnipeg, Manitoba, which instituted the change at the urging of Stephen Juba, mayor of Winnipeg at the time. Winnipeg initially used 999 as the emergency number, but switched numbers when 9-1-1 was proposed by the United States. In the United States, the push for the development of a nationwide American emergency telephone number came in 1957 when the National Association of Fire Chiefs recommended that a single number be used for reporting fires. In 1967, the President's Commission on Law Enforcement and Administration of Justice recommended the creation of a single number that could be used nationwide for reporting emergencies. The burden then fell on the Federal Communications Commission, which then met with AT&T in November, 1967 in order to come up with a solution.

In 1968, a solution was agreed upon. AT&T chose to implement the concept, but with its unique emergency number, 9-1-1, which was brief, easy to remember, dialed easily, and worked well with the phone systems in place at the time.

MANHATTAN WHITE PAGES (1967):
fire OPERATOR
police 440-1234
ambulance 440-1234
doctor 879-1000*
coast guard 264-8770
FBI 535-7700
(...)
Service Representative Dial 811
Repairman Dial 611
Information--Manhattan Dial 411

MANHATTAN WHITE PAGES (1968):
fire "0" (Operator)
police,
ambulance dial 911
(...)
911 -- A FIRST FOR NEW YORK: New York is the first major city in the nation to have this new Universal Emergency Number -- 911, the fastest way to get help in an emergency. Easy to remember, quick to dial, 911 puts you right through to the high-speed communications network of New York City's Police Department.