Compared to police badges, which have been symbols of authority since at least the mid-19th century, when tin stars differentiated the "good" guys from the "bad" ones in the Wild West, police patches are relatively recent arrivals. In fact, police patches did not become popular in the United States until the 1930s, when insignia for law-enforcement officials were hand embroidered on felt. Eventually the designs and lettering on patches for local, state, and federal peacekeepers were stitched by sewing machines, which brought uniformity to the designs and ubiquity to the genre.
Police patches can be shaped like shields, circles, triangles, and (depending on your locality) arrowheads, keystones, or an officer’s home state. Some people collect patches based on geography (for example, all the police badges in Texas) while others collect patches based on the wearer’s duties, whether they worked on a bomb squad, S.W.A.T. team, or mounted patrol. Patches showing service in a specialized units such as motorcycle patrols, divisions, or squads are generally more difficult to find (they are certainly pricier) than stock patches, which only vary from area to area by the name of the community being served. Other special-unit patches include those worn by members of Native American “tribal” police officers.
Sheriff and highway-patrol patches are highly collected, as are patches featuring elaborate embroidery (vintage patches from Alaska, Hawaii, and Florida are some of the nicest). And then there are U.S. government police patches, which range from simple patches bearing the letters M.P. for military police to more elaborate designs that herald one’s membership in the police units of the U.S. Treasury, Arlington National Cemetery, or even the Bureau of Engraving and Printing.