Immigration has contributed to many of the economic, social, and political processes that are foundational to the United States as a nation since the first newcomers arrived over 400 years ago. After brushes with immigration reform that began in 2001 and continued in 2006 and 2007, the United States seems to be on the threshold of overhauling the legal immigration system in the most substantive way since 1965. This article provides a comprehensive overview of major legislation and events affecting U.S. immigration throughout history, legal and illegal immigration flows, postrecession immigration trends, and more.

Over the past five decades, Mexicans have constituted the single largest group of immigrants to the United States originating from Latin America. In 2011, 11.7 million Mexican immigrants resided in the United States, representing 29 percent of the U.S. immigrant population and close to 4 percent of the overall U.S. population. This article examines the latest data on Mexican immigrants in the United States, including population size, geographic distribution, admission categories, and demographic and socioeconomic characteristics.