The unit cloth patch on soldiers' uniforms is over 135 years old. It was born in 1862 in the American Civil War, when General Philip A. Kearney, the hard driving commander of the Federal Third Corps, assigned badges to the divisions within his corps. This was prompted, it was said, by an occasion when he mistook some officers for men of his corps and reprimanded them about their appearances The patches worn by the Third Corps were made from cloth cut in a variety of shapes. Some of this design simplicity still exists: for example, in the red diamond patch of the 5th Infantry Division, once the patch of the Ist Division of the 5th Corps in the Civil War. The 6th and 28th Infantry Divisions in the modern US Army also retain a similar geometric simplicity. Up to World War II the lst Corps had their original round patch and the 24th Corps a heart-shaped one.

Within a year of their introduction, Corps patches had been adopted by all the Northern armies and General Hooker had assigned colors to the divisions within each Corps. The Civil War had begun with many regiments sporting colorful uniforms, but by its close these were greatly simplified and blue and gray had become standard colors. Patches were therefore a useful way of distinguishing men and their units.

However, even today the US Army retains some of the old traditions of the 1860s, with colored piping and backings on modern dress blue uniforms. The infantry have light blue, the cavalry yellow, the artillery red, and engineers white. This light blue color appears as the backing to the Expert and Combat Infantryman's badge. The tradition is still remembered in slang - the pejorative nickname for non-airborne soldiers in the US Army is 'Legs' - an abbreviation of 'Red Legs', the term which was used for artillerymen in the Civil War because of their red or red-piped trousers.

The 'shoulder patch' as it is worn today was officially introduced into the US Army in 1918. That summer, soldiers of the 81st Infantry Division embarking at Hoboken, New Jersey, wore a hand-embroidered 'wild cat' badge on the upper left arm. When they arrived in France other US Army units adopted the idea, even though it was still unofficial. Permission to wear the insignia was given on October 19, 1918.