Mara Salvatrucha (MS-13)

Mara Salvatrucha (MS-13). The group's name was apparently derived from the Spanish terms for "army units" of street-tough Salvadorans, with the "13" being a gang number from Southern California.

The MS-13 has international reach, though it is concentrated in urban areas of the United States and the Northern triangle, made up of El Salvador, Honduras and Guatemala. It has a growing presence in southern Mexico, particularly Chiapas state.

The group began as a Los Angeles-based gang,...