The United States began regulating immigration soon after it won independence from Great Britain, and the laws since enacted have reflected the politics and migrant flows of the times. Early legislation tended to impose limits that favored Europeans, but a sweeping 1965 law opened doors to immigrants from other parts of the world. In more recent years, laws and presidential actions have been shaped by concerns about refugees, unauthorized immigration and terrorism.

A 1790 law was the first to specify who could become a citizen, limiting that privilege to free whites of “good moral character” who had lived in the U.S. for at least two years. In 1870, the right of citizenship was extended to those of African origin.

Starting in 1875, a series of restrictions on immigration were enacted. They included bans on criminals, people with contagious diseases, polygamists, anarchists, beggars and importers of prostitutes. Other restrictions targeted the rising number of Asian immigrants, first limiting migration from China and later banning immigration from most Asian countries.