MS 13 means: Their violence is felt in all 33 US states. Mara Salvatrucha. The gang is unique in that it has between 8,000 and 10,000 members across 33 US states. This makes them one of America’s most popular street gangs. MS-13 was founded in Los Angeles by Salvadorans who fled civil war in the 1980s. Many children grew up in a world of violence. (in Community Dictionary, added by Maribel Wise)