First brought to the forefront of American popular culture by the Jets and Sharks in the 1961 film West Side Story, gangs have long been a part of illegal activity around the world. From the Sicilian Mafia (see entry under 1960s—The Way We Lived in volume 4) to the Chinese Tongs to the outlaws of the American frontier, gangs have brought together criminals who joined in brotherhood for strength and protection.

During the late 1940s and early 1950s, urban street gangs began to appear in the poor neighborhoods of many U.S. cities. These gangs were mostly made up of young men and women from harsh, underprivileged backgrounds who looked to fellow members for social support and physical protection. Gangs were often divided along ethnic lines. They formed to claim and protect territory from other ethnic groups and newly arriving immigrants. Gang membership in the 1950s did not always...