Aryan Brotherhood

The report, "Bigotry Behind Bars: Racist Groups in U.S. Prisons," says prison officials estimate up to 10 percent of the nation's inmates are affiliated with racist gangs that are bolstered by hate groups outside the prisons.

The ADL says the most notorious gang is the Aryan Brotherhood, which was established in the 1960s at Northern California's San Quentin Prison and has spread to prisons throughout the United States.

From 1982-1989, the FBI investigated the California prison gang known as the Aryan Brotherhood. The Aryan Brotherhood was a violent white supremacist group allegedly responsible for numerous attacks and murders of inmates and correctional officers throughout the federal and state penal system. The case was closed when the U.S. Attorney, Los Angeles, declined prosecution.