https://en.wikipedia.org/wiki/Gangs_in_the_United_States
Gangs in the United States include several types of groups, including national street gangs, local street gangs, prison gangs, motorcycle clubs, and ethnic and organized crime gangs.[3] Approximately 1.4 million people were part of gangs as of 2011, and more than 33,000 gangs were active in the United States.[4]
People join gangs for various reasons.[5][6][7][8][9][10] Some become gang members to profit from organized crime in order to obtain necessities such as food and shelter, or to gain access to luxury goods and services. They may be seeking protection from rival gangs or violent crime in general, especially when the police are distrusted or ineffective. Many are attracted to a sense of family, identity, or belonging. Other motivations include social status, intimidation by gang members, pressure from friends, family tradition, and the excitement of risk-taking.
Decker and Van Winkle (1996) view joining youth gangs as consisting of both pulls and pushes. Pulls pertain to the attractiveness of the gang. Gang membership can enhance prestige or status among friends (Baccaglini, 1993), especially girls (for boys) (Decker and Van Winkle, 1996), and provide opportunities to be with them (Slayton, Stephens, and MacKenna, 1993). Gangs provide other attractive opportunities such as the chance for excitement (Pennell et al., 1994) by selling drugs and making money (Decker and Van Winkle, 1996). Thus, many youth see themselves as making a rational choice in deciding to join a gang: They see personal advantages to gang membership (Sanchez-Jankowski, 1991).
http://www.lapdonline.org/top_ten_most_wanted_gang_members/content_basic_view/23473
https://web.archive.org/web/20080316060738/http://www.dc.state.fl.us/pub/gangs/chicago.html
https://en.wikipedia.org/wiki/List_of_gangs_in_the_United_States
USA