USA immigration refers to the movement of people from their native countries to the United States. Immigration to the US has been the country’s main source of population growth for many years. USA immigration has also changed United States history, as different cultural groups made their homes in the country and changed the course of American history. From 1892 to 1954 Ellis Island, located in the New York Harbor, served as the main immigrant processing center. Ellis Island welcomed over 12 million immigrants throughout that period-predominantly of European descent. Ellis Island signifies the historical backbone of USA immigration, and many Americans trace their ancestral roots back to that immigration processing center.

The four historical periods of USA immigration are as follows:

• Colonial period
• Mid-nineteenth century
• Turn of the 20th century
• Post-1965

Because of the high rate of USA immigration, the country is a diverse land comprised of many races and ethnicities. USA immigration remains popular, and in 2006 the United States had the most permanent residents in the world, totaling 37.5 million. High rates of immigration, however, have not been without controversy. Some maintain that USA immigration results in high levels of criminal activity, with a large number of immigrants in jail, and that immigrants pose a drain on social services and related funding. The US has made recent efforts to control illegal immigration, including constructing a fence surrounding the U.S.-Mexico border. Many immigration advocates decry the construction of the border fence and maintain that the United States is a country founded by immigrants, and they encourage the country to remain “immigrant-friendly.”