There were an estimated 30 million surveillance cameras in the United States in 2011 . Video surveillance has been common in the United States since the 1990s ; for example , one manufacturer reported net earnings of $ 120 million in 1995 . With lower cost and easier installation , sales of home security cameras increased in the early 21st century . Following the September 11 attacks , the use of video surveillance in public places became more common to deter future terrorist attacks . Under the Homeland Security Grant Program , government grants are available for cities to install surveillance camera networks . In 2009 , there were an estimated 15,000 CCTV systems in Chicago , many linked to an integrated camera network . New York City 's Domain Awareness System has 6,000 video surveillance cameras linked together , there are over 4,000 cameras on the subway system ( although nearly half of them do not work ) , and two-thirds of large apartment and commercial buildings use video surveillance cameras . In the Washington D.C.-area , there are more than 30,000 surveillance cameras in schools , and the Metro has nearly 6,000 cameras in use across the system
September 11 attacks
September 11 attacks
Closed-circuit television