For nearly 150 years, the Supreme Court has denounced jurisdictional ambiguities in immigration policy, regularly striking down state laws as unconstitutional intrusions on the federal government’s “broad, undoubted power.” Most scholarship on the historical evolution of US immigration policy has followed suit, rendering invisible the role of state governments and federalism in immigration policy during the crucial, transformative decades of the Gilded Age and the Progressive Era. This article redresses these silences by spotlighting the aggressive state policy activism and critical intergovernmental negotiations over how to control immigration and noncitizens from the 1870s to the 1920s. Focusing on two older, eastern seaboard states—Maryland and Virginia—and two newer, southwestern states—Arizona and New Mexico—these historical case studies show how subnational immigration initiatives were fueled by distinctive local and regional labor need and racial landscapes. This article also identifies and illuminates distinct forms of autonomous, interdependent, insistent, and validated activism by states in immigration federalism.