The Sur 13 gang is part of a larger affiliation of gangs called the Surenos. The Surenos are a national Mexican-American gang in the United States with a heavy presence in California.
California has the largest Surenos gang presence, but the group also has members in Texas, New Mexico, Arizona, Nevada and North Carolina. The Surenos are associated with drug-trafficking organizations in Mexico, such as the Gulf Cartel crime syndicate.
The Surenos work with the Mexican Mafia, a criminal prison organization. The word "sur" means "south" in Spanish, and the gang uses the number 13 to represent the letter M, the 13th letter of the alphabet. They use the M to pledge allegiance to the Mexican Mafia. Sureno members have the word "Sureno" is tattooed onto themselves to validate their gang membership. Other common gang markings include XIII, X3, 13, uno tres and Sur13.
The Sureno gang takes part in crimes such as homicides, human trafficking, drug trafficking, kidnapping and assaults. However, the main objectives of the gang are to carry out orders from the Mexican Mafia and distribute illegal narcotics. When Sureno members are asked what being a Sureno gang member entails, they repeat the mantra, "A Sureno is a foot soldier for the Mexican Mafia."