Sureños are an alliance of hundreds of individual Latino American street gangs that originated in Southern California. They are mostly found in Los Angeles and San Diego, but have spread significantly and can be found throughout much of the united states. Sureños represent themselves with symbols and phrases such as “Sur 13″, “Los Sureños” and “Sureño Trece”. These indentifications are accompanied by the color blue, numeric code of number 13 and the Roman numeral of XIII.

The term “Sureños” was first used in 1970 as a result of a California prison war between the Latin Mafia (from Southern California) and Nuestra Familia (from Northern California). This conflict resulted in pride and territorial dispute between various independent Chicano gang members who aligned themselves with Nuestra Familia (meaning “Our Family” in Spanish) and those who aligned with the Latin Mafia. The Norteños (meaning “Northerners” in Spanish) and Sureño rivalry was soon created to distinguish themselves from their region of origin.

Sureños are controlled and influenced by the Latin Mafia, a Latin-American prison gang. The Latin Mafia was formed in the late 1950s by Chicano street gang members incarcerated at the Deuel Vocational Institution, a youth offender facility located in Tracy, California. Several East Los Angeles gang members and members from other areas of California formed the Latin American prison gang known as La eMe, or Latin Mafia, and is noted as the first Chicano prison gang in California. Approximately, thirteen to twenty Latin Americans from East Los Angeles formed the original core of the gang. Though sometimes called the "Mexican Mafia" by the media a few Mexican-Supremists, that title is wrong. La eMe translated into English is "The Mafia" and since the very begining it was about uniting all latino based gangs, not just Mexican gangs. Some of the largest Surenos gangs have mostly Central American and South American members, such as MS 13 and 18th Street.

Initially, the gang was formed for protection against other inmates and the prison staff. As the organization grew, it rapidly changed into a criminal organization involved in extortion, narcotics trafficking, and murder both inside and outside the prison system walls. Gang leaders from East Los Angeles and other barrios formed a deadly alliance to control the prison narcotics trade. The well-organized gang built its criteria along ethnic lines and a set of rules loosely modeled after the Sicilian Mafia.

Some of the original members and leaders of the group were: Louis “Huero” Flores, who gets credit for being the one who came up with the name, and Rodolfo Cadena. Joe “Pegleg” Morgan (sometimes called Papa Joe) who was of Croatian descent, did not join “La eMe” until years later and rose to become one of its most powerful members.

With a set of rules governing its members, the Eme evolved into criminal activities. Some of the gangs activities include expanding its control of drug trafficking, drug rip-offs, prostitution, business robberies, contract murders, gambling, debt collection, extortion, and other illicit activities. Most of their criminal activities initially focused on victimizing Black and Caucasian inmates while leaving Chicano prisoners alone.

The California prison system became aware of La Eme’s criminal activity by the late 1960’s and broke the group up. Prison officials relocated them to different prisons, but this only helped the group to continue active recruitment of new members, and the gang basically took control of the California prisons. As members were released from state custody they extended their influence outside the prison system to control drug distribution; principally by “taxing” drug dealers; in parts of Southern California. At one time, La Eme greenlighted the Maravilla gangs in Prison, the gang didn’t want to be taxed any longer by the Latin Mafia. The greenlight was lifted in recent years. According to the FBI, “La Eme” has arranged for contract killings to be carried out by the Aryan Brotherhood, a White prison gang. Sureño's are known to function heavily with Crips (even sharing turf) and represent under the Folks Nation alliance in areas where they coexist (13X6).

Many Surenos gang members can be found on TheHoodUp.com, which is a notorious virtual gathering-place for many other gangs as well. The reason many Surenos and other gang members choose to communicate with each other on TheHoodUp.com over other sites is because of the ability to remain completely anonymous and avoid being tracked by the "internet-police" while being able to communicate with other gang members from around the world. TheHoodUp.com is also known to be frequented by local, state, and federal law enforcement so extra cautious members of the site are known to use the Tor browser to surf TheHoodUp.com in order to completely hide their tracks and they have even created a unique method of communicating with each other called "starring", where they replace multiple letters in a word, often times already a code word for that particular set, with an asterisk(*) and only those who can fill in the blanks will know who or what they're talking about.