His research and teaching investigates the paradoxes of democracy and inequality in the 19th and 20th century United States and Canada. He approaches the history of western North America in the 19th and 20th centuries as a place where ethnic, national, gender and sexual identities, communities and practices are forged and recreated through the forces of capitalist political economy, competing state formations and the cultural and social transformations of migration. He explores the waves of Asian migrations along the Pacific Coast of North America and the U.S.-Mexican border region.