Police uniforms in the United States vary widely due to the nation's tradition of highly decentralized law enforcement. Over time, however, a number of general conventions and styles have become representative of American police fashion. Police officers wear uniforms to deter crime by establishing a visible presence while on patrol, to make themselves easily identifiable to non-police officers or their colleagues who require assistance, and to quickly identify each other at crime scenes for ease of coordination.
Individual municipal and county law enforcement agencies in the United States are typically responsible for designing their own uniforms, often with minimal state regulation. As a result, there is no universal form or pattern for American police uniforms.
However, in general, most large police departments provide officers with two types of uniforms for wear, tactical (also called "Class B"), and traditional (or "Class A"). Tactical uniforms - similar in material and cut to the U.S. Army's former battle dress uniform - are generally worn while on patrol, or performing physically intense duties, while traditional-style uniforms are more often used for station assignments, high profile events, and ceremonial functions. In addition to these two basic uniform types, a variety of specialized clothing may be deployed as necessary, including jumpsuits (sometimes called "Class C") and - in the case of police pipe bands - highland dress. Many police departments restrict the use of tactical uniforms to tactical units, such as SWAT teams, or for special assignments, such as riot control, in order to present a less militarized appearance in day-to-day operations. Municipal police uniforms are typically colored in blue or black, while uniforms worn by sheriff's deputies are more often brown and khaki. Unlike British police, American law enforcement agencies do not usually include white-colored apparel, such as shirts, in their uniforms due to the fact white reflects in the dark and can make police officers more prominent targets for armed criminals during building searches or standoffs. There are, however, many exceptions to this general rule; the Miami Police Department wears white uniform shirts, and senior officers in the New York City Police Department, Baltimore Police Department, and Philadelphia Police Department have uniforms that also feature white shirts.