Established in 1935, the New York City Transit Police Department was responsible for the protection of New York City Subway lines for 60 years. In 1949 the department was officially divorced from the NYPD, but was eventually fully re-integrated in 1995 as the Transit Bureau of the NYPD by New York City Mayor Rudolph Guiliani. It is now largely incorporated into the NYPD's Transportation Bureau.

One task of the Transit Police is its defense of the subway system from defacement. Graffiti was very prominent throughout the subway system by the mid-1980s and the city government took a hard line in response, though some saw it instead as a "social trend" and a sign of diversity. The Transit Police, and specifically a new unit called the Vandal Squad began to fine and arrest those painting graffiti. They also made a policy to remove any work of graffiti within 24 hours of its creation.

By the end of the '80s the Transit Police had effectively solved the problem of graffiti in the subway system. To this day the Vandal Squad exists to prevent "the look of disorder" from over-running the city.