My first book, _Borderline Americans: Racial Division and Labor War in the Arizona Borderlands_ (Harvard University Press, April 2009, paperback 2011), explores the changing meanings of race in America through the microcosm of southeastern Arizona's mine and ranch country. More recently I have published articles on immigration history and Arizona border politics. My current research examines the history of the U.S. Congress's Dillingham Commission, which conducted a massive study of immigration in the early twentieth century. Its findings paved the way for the immigration restrictions of 1920s that ended mass migration to the United States until the 1960s.