[4] In 1940, with increasing concern about national security, immigration and naturalization was organized under the authority of the Department of Justice.

Its officers inspected foreigners arriving at an official Port of Entry (POE), detecting and deterring illegal entry between the ports (with the assistance of the Border Patrol, a component of the INS) and by sea, and conducting investigations of criminal and administrative violations of the Act.

The INS also adjudicated applications for permanent residency ("green cards"), change of status, naturalization (the process by which an alien [foreign-born person] becomes a citizen), and similar matters.

The Field Operations division implemented policies and handled tasks for its three regional offices, which in turn oversaw 33 districts and 21 border areas throughout the country.

The Office of Policy and Planning coordinated all information for the INS and communicated with other cooperating government agencies and the public.

[1] After World War I, Congress attempted to stem the flow of immigrants, still mainly coming from Europe, by passing a law in 1921 and the Immigration Act of 1924 limiting the number of newcomers by assigning a quota to each nationality based upon its representation in previous U.S. Census figures.

[7] By July 1941, Justice Department officials had decided that the INS would oversee the internment of enemy aliens arrested by the FBI should the U.S. enter the war, and immediately after the attack on Pearl Harbor these plans went into effect.

[8] These "enemy aliens," many of whom had resided in the United States for decades, were arrested without warrants or formal charges.

They were held in immigration stations and various requisitioned sites, often for months, before receiving a hearing (without the benefit of legal counsel or defense witnesses) and being released, paroled, or transferred to a Department of Justice internment camp.

Films using its work as a theme include The Immigrant (1917), The Strong Man (1926), Ellis Island (1936), Paddy O'Day (1936), Gateway (1938), Secret Service of the Air (1939), Exile Express (1939), Five Came Back (1939), Illegal Entry (1949), Deported (1950), Gambling House (1951), Coneheads (1993), My Fellow Americans (1996), Men in Black (1997), Fun with Dick and Jane (2005) and Ip Man 4: The Finale (2019).