First seen on the U.S-Mexican border, the NYPD now deploys Sky Watch towers as part of its crime-fighting efforts.

On Camera: Surveillance In Transit, Schools

A 1998 New York Civil Liberties Union survey identified 2,397 surveillance cameras at street level in Manhattan. In 2005, another NYCLU survey of Lower Manhattan, Greenwich Village, Chinatown and central Harlem found 4,468 cameras in those four districts alone.