Who has the right to enter U.S. territory, move across it, and settle here? In the 19^th century, the U.S. federal system made it difficult for politically unpopular groups to migrate and remain by giving migration control to the states. It took over a century for the federal government to gain control of migration policy in the late 19^th century, but nationalization did not result in freer movement. This Constitution Day talk analyzes how the constitutional text interacted with the politics of a different era to shape the content and trajectory of U.S. migration policy.