The "boys in blue" are no longer just boys, but the color of their uniforms has stayed consistent since the first modern police forces appeared in the 19th century. In the U.S., the UK, and other countries, cops can be identified by their dark navy clothing. Though the design does serve a real purpose, it was mainly chosen because it was what was available at the time.
According to Police1, blue police uniforms originated in London. The London Metropolitan Police is considered the first real police force, and when it was established in 1829, officers were given dark blue garments to wear. Because British soldiers were already wearing red and white during this era, blue was picked to distinguish cops from the military.
The United States' first official police force was formed in New York in 1845, and blue uniforms in the style of London's bobbies soon became the standard. When cities like Boston, Philadelphia, and Detroit began employing police officers, they adopted blue uniforms as well.
In some cases, American police units chose the color for totally opposite reasons than the UK. During the Civil War, blue Union Army outfits were easy to come by, and the extras often went to police forces that didn't have official uniforms yet. This is how the Los Angeles Police Department first began dressing in blue. After the war, the color stuck around.
Today, police officers wear blue for practical reasons. The dark navy color makes them harder to spot when tracking down suspects at night. The color is also better at hiding stains than a lighter shade would be. Not all police uniforms come in the same color—some officers wear black or dark green—but dark blue is the shade mostly closely associated with the profession.
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