
No, not an alien from outer space, but a non-naturalized immigrant living in the United States!
Registering aliens in the U.S. started as early as 1798 and happened on and off until 1940, when the Immigration and Naturalization Service (INS) required each alien to register and obtain a registration number at their local post office. Only 1 million were expected to respond to the request, but more than 5 million actually registered. In April 1944, these alien registration numbers were used to create individual case files called Alien Files or A-Files for aliens that had correspondence with the INS.
A-Files exist for those that:
- Registered in 1940 and had some communication with the INS after 1 April 1944
- Immigrated after 1 April 1944 but did not naturalize prior to 1 April 1956
- Naturalized after 1 April 1956
Last month I visited the National Archives at Kansas City, Missouri (Central Plains Region) to view some A-Files to see what they contained. These A-Files were sent to Kansas City in 2009 from the United States Immigration and Citizenship Services (formerly the INS). They can be rich with information about your ancestor. The alien registration form can include the alien’s name, the name they entered the United States with, their birth date and place, physical description, when they last arrived in the United States, and even their fingerprint!

For example, on Nicholas Polanski’s alien registration form, he stated he was born 5 Feb 1884 in Premisliensis, Brozozow, Austria. He entered the United States on 12 Dec 1905 through New York on the vessel Keiser Wilhelm. He was then living in Wheeling, Ohio working as a coal miner.
To determine if your ancestor had an A-File, search the National Archives Archival Research Catalog (ARC). Follow these steps:
- Below the search button, click on Advanced Search.
- In the “with all of the words” field, type “Alien Files”
- You will get a list of all records pertaining to Alien Files in their database. The first result is: “Alien Case Files, compiled 1944-2003.” Click on this link.
- This will bring up a description of the collection. About half way down the page you will see “Includes”. At the end of that line it says, “Search within this Series.” Click on the link.
- Type in the name and do a search.
- Once you have found your person, you can request a copy of this file from the National Archives in Kansas City, Missouri.
For more information on United States naturalization policies and records, see the United States Naturalization and Citizenship article in the FamilySearch Research Wiki.