Immigration to the United States of America refers to the movement of non-residents to the United States. Even though the foreign born have never composed more than 16% of the U.S. population since 1675 , immigration has been a major source of population growth and cultural change throughout much of American history. The economic, social, and political aspects of immigration have caused controversy regarding ethnicity, religion, economic benefits, job growth, settlement patterns, impact on upward social mobility, levels of criminality, nationalities, political loyalties, moral values, and work habits. As of 2006, the United States accepts more legal immigrants as permanent residents than any other country in the world. In 2006, the number of immigrants totaled 37.5 million.

Given the distance of North America from Eurasia, most historical U.S. immigration was risky. International jet travel has facilitated travel to the United States since the 1960s, but migration remains difficult, expensive and dangerous for those who cross the United States–Mexico border illegally.

Recent immigration-related proposals have suggested criminalizing illegal immigrants, building a barrier along some or all of the U.S.-Mexico border, and creating a new guest worker program. Through much of 2006, the country and Congress was immersed in a debate about these proposals. As of March 2007, few of these proposals had become law, though a partial border fence was approved. Many cities, including Washington D.C., New York City, Los Angeles, Chicago, San Francisco, San Diego, Salt Lake City, Phoenix, Dallas, Houston, Detroit, Jersey City, Minneapolis, Miami, Denver, Baltimore, Seattle, Portland, Oregon and Portland, Maine, have adopted “sanctuary” ordinances banning police from asking people about their immigration status.