
For those of us whose ancestors immigrated to the United States in the 20th century, your ancestors might have had to register with the federal government as an alien. If so, those records can yield genealogy gold! This is the first post in a new series about researching your immigrant ancestors’ alien registration documents.
Terminology
When I teach about U.S. immigration history, I always start out by clarifying my use of the term alien. Alien is the legal term for a United States immigrant who has not naturalized and become a U.S. citizen. The term first appears in U.S. immigration-related laws in the Naturalization Act of 1790, the first law to define how a foreign-born immigrant could acquire U.S. citizenship through naturalization.1 The term immigrant is not specific enough because immigrants can become U.S. citizens, and they still remain immigrants after naturalization.
I personally do not like the term alien. I think it is a dehumanizing word, and it has become a very political and polarizing word. However, alien is a legal term, and we genealogists need to understand the terminology in the laws that applied to our ancestors and in the records that name our ancestors.
The Alien Registration Act of 1940
The U.S. Congress passed the Alien Registration Act on 28 June 1940 as a national security measure. Although the U.S. did not enter the war until 8 December 1941 – after Japan bombed Pearl Harbor – hostilities in Europe began on 1 September 1939 when Germany invaded Poland. Title I of this act outlawed certain subversive activities, such as advocating for the overthrow of any level of government in the U.S.2 Title II amended earlier laws pertaining to the admission and deportation of aliens, such as now denying admission to any alien who is a member of anarchistic organizations.3 Title III is the section of the new law that pertained specifically to alien registration.4
Applicable Individuals
The new law required all aliens living in the U.S. for 30 days or longer as of 27 August 1940 to register with the federal government. However, the law exempted foreign government officials and their family members from this requirement. The registration process involved filling out a form, being fingerprinted, and testifying to the accuracy of the information in that form. Aliens age 14 or older had to register for themselves. Parents or legal guardians had to register on behalf of alien children under age 14.
Newly arriving aliens:
- They had to register at the nearest consulate.
- A visa would not be issued without registering.
Aliens who recently arrived:
- Every alien age 14 or older who planned to be in the U.S. for 30 days or longer had to apply for registration before that 30 days expired
- Aliens under age 14 who planned to be in the U.S. for 30 days or longer had to have each of their parents or legal guardians apply for registration for that minor child before the 30 days expired. Upon their fourteenth birthday, each minor alien had to apply for registration for themselves within 30 days of that birthday.
Aliens already living in the U.S. longer term:
- Every alien age 14 or older had to apply for registration by a designated date. This pertained to all non-naturalized aliens even if they had already taken out first or second papers for naturalization.
- Aliens under age 14 had to have their parents or legal guardians apply for registration for that minor child by a designated date. Upon their fourteenth birthday, each minor alien had to apply for registration for themselves within 30 days of that birthday.
The Alien Registration Program
This new federal law led to a three and a half year long program – the Alien Registration Program – to create a national registry of all resident aliens already living in the United States or arriving to the U.S. after the start of this program. The commissioner of the Immigration & Naturalization Service (INS) oversaw the program and registry.
Where, How & When to Register
Each applicable resident alien had to register at their local post office. The law placed responsibility on the postmasters – who could designate their staff – for registering and fingerprinted each applicant. The postmaster then forwarded the registration forms to the Department of Justice in Washington, DC. The INS commissioner could appoint other registration locations and INS employees to process the registrations.4 The program was designated to begin 27 August 1940. All applicable resident aliens had to register by 26 December 1940 in the initial registration phase.6
Those who chose not to register or filed known false information in their application could be fined up to $1,000 or imprisoned if convicted. The law required registered aliens to notify the INS commissioner of their address every three months and within five days after moving to a new address. Otherwise they could be fined or imprisoned.7
How They Knew to Register
Newspapers throughout the U.S. announced the new Alien Registration Act and the registration program, to whom it applied, where and how to register, and the registration dates. These newspaper announcements stressed that registrants would not have to pay any fees. Following is the headline and opening paragraph of an article in the 26 August 1940 issue of the New York Times announcing that national registration would start the next day and go through 2 December 1940.8

This announcement ran in the New York Times the day before national registration was scheduled to start.
Foreign language newspapers in the U.S. would have been a critical way in which our immigrant ancestors learned about the new law and registration program, explained in their native language. My Mexican immigrant great-grandmother, her two oldest children born in Mexico, her mother (my 2nd great-grandmother), and the many members of their immigrant extended family network living in Los Angeles County would have read this 9 August 1940 article in La Opinión [The Opinion], the Spanish-language newspaper founded in Los Angeles. Like the New York Times article, this one stressed that registrants would not have to pay any fees to comply with this new law.9

This 9 August 1940 article in La Opinión explains the new alien registration will take place 27 August to 26 December 1940.
Our immigrant ancestors also likely learned about the new law and required alien registration at their workplaces. The New York Times announcement, which possibly contains boilerplate text sent in a press release by the INS, recommended that employers post noticed at their places of business and allow relevant employees to have time off from work to go register.8

The Registration Form
Registrants were required to fill out a designated form, an Alien Registration Form (AR-2 Form). Temporary forms (AR-1 Forms) were available at post offices and resident aliens were encouraged to pick up a temporary form ahead of time to review and fill out at home before showing up for official registration to fill out the permanent AR-2 version of the form in person. If the registrant brought a temporary form to the post office on registration day, a stenographer copied the information from the temporary form to the permanent form while the registration had their fingerprints taken.11
The AR-2 form consisted of 15 sets of questions pertaining to the background and activities of the resident alien. The individual had to swear to the accuracy of the information, be fingerprinted, and then sign their name. When they INS received the AR-2 form, they assigned a unique Alien Registration Number (AR# or A#) to the individual, which followed that individual until naturalization – if they became a US. citizen – or until death. The INS then mailed the registrant an Alien Registration Card to keep as proof of registration.


The document above is the Alien Registration Form (AR-2 Form) for my great-aunt Maria Guadalupe “Lupe” Robledo Nieto, who at this time in 1940 went by Guadalupe Mary as her given name and her married surname of Perez.
We will go over the form more in-depth in the next post of this series and explain where and how to find the Alien Registration Forms for your 20th century ancestors.
Sources
- U.S. Congress, United States Statutes at Large, volume 1, 1790 (Boston: Charles C. Little and James Brown, 1845), p. 103. ↩
- U.S. Congress, United States Statutes at Large, volume 54 (Washington D.C.: Government Printing Office, 1941), p. 671, “Alien Registration Act, 1940.” ↩
- Ibid. ↩
- U.S. Congress, United States Statutes at Large, volume 54 (Washington D.C.: Government Printing Office, 1941), p. 674, “Alien Registration Act, 1940.” ↩
- U.S. Congress, United States Statutes at Large, volume 54 (Washington D.C.: Government Printing Office, 1941), p. 674, “Alien Registration Act, 1940.” ↩
- “Alien Registration,” New York Times, 26 August 1940, page 14, column 3; imaged, ProQuest Historical Newspapers: New York Times (https://www.proquest.com/hnpnewyorktimes/docview/105392576/ : accessed 18 January 2026). ↩
- U.S. Congress, United States Statutes at Large, volume 54 (Washington D.C.: Government Printing Office, 1941), p. 675, “Alien Registration Act, 1940.” ↩
- “Alien Registration,” New York Times, 26 August 1940. ↩
- “El 27 Empieza el Registro de Extranjeros {Alien Registration Begins on the 27th}, La Opinión {The Opinion}, 9 August 1940, page 2, column 5; imaged, California Digital Newspaper Collection (https://cdnc.ucr.edu/?a=d&d=LO19400809.2.23 : accessed 18 January 2026). ↩
- “Alien Registration,” New York Times, 26 August 1940. ↩
- “Los Angeles Starts to Count Its Alien Population: Five Hundred Aliens Register.” Los Angeles Times, 29 August 1940, page A1; imaged, ProQuest Historical Newspapers: Los Angeles Times (https://www.proquest.com/hnplatimes/docview/165097842/pageviewPDF/9D7305F711A44BD6PQ : accessed 19 January 2026). ↩
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