The New York City Police Department (NYPD) , the largest police department in the United States, has primary responsibility for law enforcement and investigation within the five boroughs of New York City. It is considered to be the first "modern" style police department in the United States; when it was created in the 19th century, it was modeled after London's Metropolitan Police.
The New York City Transit Police and Housing Police were fully integrated into the NYPD in 1995; some new police officers are randomly assigned to the Transit and Housing units.
The Compstat program, introduced under then-Commissioner Bill Bratton in the 1990s, uses statistics about crime rates and arrests to evaluate police precincts and commands. As of June 2003, there are charges that some precinct commanders have been falsifying crime reports and other data to make the statistics for their areas look better.
The size of the force has fluctuated, depending on crime rates, politics, and available funding. In June 2004, there were about 40,000 sworn officers plus several thousand support staff.
The NYPD is headed by the New York City Police Commissioner with the senior sworn officer being titled the Chief of Department. It is divided into 10 bureaus. Each is headed by a Bureau Chief, with the Detective Bureau being headed by the Chief of Detectives.
Police Commissioner Raymond J. Kelly is the 41th Police Commissioner of the City of NewYork.
Police Officers have been officially carrying firearms while on duty since 1887, Rule 503 of the "Manual of Rules and Regulations" stated: "In addition to the ordinary baton of the patrolman each member of the Police Force shall be armed while on duty with a revolving pistol of pattern and caliber approved by the board."
In 1901 the department rule changed to "each, member of the patrol force shall be armed on duty with a revolving pistol of.38 caliber…stamped with a number corresponding to the shield number of the officer." Officers of the force were exempt from the new rule and allowed to continue carrying their.32 caliber revolver.