青幫
Shanghai became a favourable place for criminal activity, and the Green Gang in particular, due to several factors. As the Grand Canal fell out of use for grain shipments, replaced by the sea route, Shanghai became an important transshipment point for grain; at the same time, as one of the treaty ports, it was a gateway for foreign trade, including in opium. The presence of the Shanghai International Settlement and the French Concession, which were under different jurisdictions and administrations, also made for a disjointed legal environment that favoured organised crime. Finally, massive Chinese immigration into Shanghai meant that associations based on common ancestral hometowns or sworn loyalties became important factors of Shanghai social life, and the Green Gang worked through these networks. For example, Du Yuesheng, who would become one of the most prominent Green Gang leaders in Shanghai, was introduced to Huang Jinrong, an earlier leader, because his mentor was a native of Suzhou like Huang.