In the 1800s, most large cities used call boxes for beat officers to communicate with headquarters. Before the telephone was invented in 1875, these boxes contained specialized telegraph equipment that notified the station of a crime. By 1880 most departments had replaced the telegraphs with telephones.

Britain implemented the first known three-digit emergency telephone system. Today, more than 200 countries and dependencies have universal three-digit emergency numbers.

Radio manufacturers were experimenting with two-way police radios prior to WWII, but then shifted to war production and perfected the functionality with extensive use by air and ground troops.

The development of the APCO Ten Codes for police began in 1937 to reduce use of speech on the radio at a time when police radio channels were limited. Preceding each code with “ten-” gave the radio transmitter time to reach full power. An APCO Bulletin from January 1940 included a standardized set of ten codes. The Ten Codes (or Signals) were included in APCO Project 2 (1967) and revised in APCO Project 14 (1974).

In November 1967, the FCC met with the American Telephone & Telegraph Company (AT&T) to find a means of establishing a universal emergency number that could be implemented quickly.

In the early 70’s, AT&T began developing specialized 911 features, including selective routing, automatic location identification (ALI) and automatic number identification (ANI), which came to be known as enhanced 911.

In March 1973, The White House’s Office of Telecommunications issued a national policy statement which recognized the benefits of 911, encouraged the nationwide adoption of 911, and provided for the establishment of a Federal Information Center to assist units of government in planning and implementation.

By the end of 1976, 911 was serving about 17% of the population of the United States. In 1979, approximately 26% of the population of the United States had 911 service, and nine states had enacted 911 legislation. At this time, 911 service was growing at the rate of 70 new systems per year. By 1987, those figures had grown to indicate that 50% of the US population had access to 911 emergency service numbers.

1977, 911 services starts in Lebanon County, PA.

In 1979, approximately 26% of the population of the United States had 911 service, and nine states had enacted 911 legislation. At this time, 911 service was growing at the rate of 70 new systems per year. By 1987, those figures had grown to indicate that 50% of the US population had access to 911 emergency service numbers.

From the late 1990s to the present, the way people communicate changed dramatically, from wired telephones limited to homes and offices to multi-featured smartphones that take pictures and videos and allow people to send text messages as well as place calls. This created challenges for the industry since cell phones weren’t equipped with ANI and ALI like residential phones were.

The FCC issued the Wireless Enhanced 911 Rules, which established rules for providing location information from wireless calls to 9-1-1. It ordered wireless carriers to provide the service in two phases. Under Phase I, wireless carriers had to deliver the 9-1-1 caller’s voice and originating cell site location to the most appropriate PSAP. Under Phase II, carriers had to provide more accurate location information of callers, but location estimates could be off by hundreds of meters or more.

President Clinton signed the Public Safety Act of 1999 that officially established 9-1-1 as the nation’s emergency calling number.

At the end of the 20th century, nearly 93% of the population of the United States was covered by some type of 911 service. Ninety-five percent of that coverage was Enhanced 911. Approximately 96% of the geographic US is covered by some type of 911.

In the year 2000, approximately 150 million calls were made to 911.

In 2009 Black Hawk County, Iowa, became the first area to accept text messages to 911. By 2017, some jurisdictions in nearly all states offered SMS-based text-to-911 messaging. In addition to serving as a vital tool for the deaf and hard of hearing community, text-to-911 from cell phones has become an important alternative for victims of domestic violence and suicidal persons who are not comfortable making a voice call to connect with public safety telecommunicators.

Today, about 95% of the United States has 911 access. Of that number, 95% of the 911 service is enhanced (selective call routing with number and location identification).

Legislation has already passed in many states requiring cell phones to be compliant with local indexes for the enhanced 911 system by 2004. This means any cellular telephone that dials 911 should be able to identify its number to the system and be located within a hundred yards or less.