The first naturalization law in the United States in 1790 limited citizenship to "free white persons," which set up a relatively broad and inclusive definition of "whiteness." However, the definition of whiteness narrowed such that it applied only to Anglos by the early twentieth century. What social change led to this increasingly exclusive definition of whiteness?
a. the surge in immigration of non-Anglo Europeans to the United Statesb. the migration of African Americans from the South to the Northc. the establishment of the one-drop ruled. the Supreme Court's 1896 Plessy v. Ferguson decision