The history of Mexico-U.S. migration is characterized by a series of discrete phases during which levels and patterns of migration change primarily in response to shifts in U.S. policies. The late 1990s witnessed the onset of the latest shift, moving Mexican immigration from the era of contradiction to the era of marginalization. At present a large majority of Mexicans living in the United States lie outside the full protection of the law during a period in which the penalties for illegality have grown and the persecution of unauthorized immigrants has reached record levels. Increasingly Mexicans in the United States cut off from their homeland by a militarized border but estranged from American society by anti-immigrant policies, practices, and attitudes, putting them in an unusually marginalized and vulnerable position.