Professor Johnson's work focuses on urban social relations in late nineteenth-and twentieth-century America. She teaches courses on social movements, urban and working-class history, violence, and the American West. Her earlier work looked at internal migration during World War II, police brutality, and violence on the mining and cattle frontiers. Her latest book, The New Bostonians, explores the history of new immigrants in greater Boston since the 1960s. She is now launching a digital history project and website on Boston area immigration.