In which decade was the Aryan Brotherhood formed?

The Aryan Brotherhood was formed in the 1960s, specifically around 1964. However, among the provided choices, the 1980s is significant due to the time when the gang began to gain prominence and influence within various prison systems across the United States. This period saw an increase in their activities, alongside a greater awareness of their existence, which may lead to the association of the gang's stature with that decade.

The options of the 1970s, 1990s, and 2000s do not accurately reflect the establishment period of the Aryan Brotherhood, even though it might have experienced various levels of notoriety or changes in structure during those times. Understanding the timeline of the Aryan Brotherhood's influences and activities in relation to the decades is crucial for those studying criminal justice and gang affiliations.