In the 18th century, American colonists were responsible for protecting their communities from crime and enforcing the laws that existed in those early days. The growth of America's population in the 19th century gave rise to densely populated cities and with that came more crime. Municipal police departments were created to patrol areas and protect citizens but they were outnumbered and could only do so much. More services to prevent crimes needed to be added to keep people safe.
The first private security agency in the United States was formed in the 1850s by Allan Pinkerton, a former Chicago detective, who partnered with an attorney from Chicago. Known as the Pinkertons, they prevented train robberies. Around this time Edwin Holmes created the first burglar alarm and by 1866, these alarms were protecting hundreds of customers in New York. Holmes and his son innovated the alarm's technology by connecting it to a clock and later, when telephones were invented, connecting it to the telephone network to transmit alarm signals.
American District Telegraph (now known as ADT) was founded in 1874, in direct competition with the telephone company. When alarms sounded, they sent messenger boys to the alarm sites. These messengers would then use call boxes to contact police or firefighters. Over the years the company expanded to offer security patrols among its services. ADT dominated the market for central-station alarm services by the 1960s; in 1964, the U.S. Justice Department determined that the company was operating a monopoly in restraint of trade, and forced ADT to adopt a uniform national price list and service offerings. In 1997, Tyco International purchased ADT and in 2012, ADT was again introduced as an independent, publicly traded company.
Brink's was founded in 1859 by Perry Brink in Chicago, starting as a parcel delivery company and expanding to include money transport for banks by the 1890s. In the 1920s Brink's experimented with using converted school buses as armored vehicles for transport services. After World War II, the company ramped up its security by using heavily armored cars and operators with heavy weaponry. In the 1980s, Brink's started offering home security alarms, a business that was eventually taken over by ADT. The Wells Fargo Armored Security Corporation, which was later absorbed into Loomis Armored, was also a spin-off from a delivery service.
Another security system company is G4S Secure Solutions, established in 1954 by George Wackenhut and three other former FBI agents. The company initially specialized in security services for government installations such as the Kennedy Space Center, later expanding into for-profit prison operations.
Since the 1990s, the security system services industry has grown. As of 2016 the security alarm services industry generates $23 billion in revenue and is projected to have steady growth in the coming years, as reported by the market research group IBISWorld. Today there are 56,549 security alarm service businesses in the United States.