Streetgang first seen in Los Angeles in the late 1980's.
La Mara Salvatrucha (MS, MS-13), is composed primarily of El Salvadorian immigrants who fled civil war in their home country. It was originally formed by members of the La Mara gang of El Salvador and the Farabundo Marti National Liberation Front (FMNL), a paramilitary rebel group.
MS is known to be involved in gun-running, as well as more pedestrian gang activities like drug trade, murder, extortion, rape, etc. Worth mentioning is the fact that MS is usually regarded (by those in law enforcement) as particularly violent and well-organized.
La Mara Salvatrucha currently has a strong (and growing) presence in the less affluent south shore areas of Long Island, NY, as well as presence in California, Washington, DC, Oregon, Alaska, Texas, Nevada, Utah, Oklahoma, Illinois, Michigan, Maryland, Virginia, Georgia, Florida, Canada, and Mexico.
"Por vida en la Mara Salvatrucha" is a commonly heard phrase among members.