Group work evolved from informal community organizations in the late 19th/early 20th century United States in response to industrialization, immigration, and urbanization. It was used by settlement houses, youth organizations, unions and others to help communities adapt. In the 1920s, thinkers recognized its potential and it became a recognized method. After World War II, literature and theories on group work increased and it professionalized although its popularity declined in the 1960s. It reemerged in the 1970s and continues globally with adaptations to different contexts.