MS-13 - The gang that scares other gangs. Theyâre known as MS-13, MS, Mara or Mara Salvatrucha, but by any name, theyâre trouble. MS-13 is a Central American gang founded in Los Angeles in the 1980s by Salvadoran immigrants. While still heavily represented in California, they have spread across the nationâinto at least 42 states and Washington, D.C.-- and beyond, especially into Central America.