Daily AncestorA-number
An A-number is the alien registration number the U.S. gave each noncitizen from 1940 on, written as the letter A plus a string of digits.
The numbers began with the 1940 alien registration and were stamped on each Form AR-2. From April 1, 1944, the same number labeled the person's A-File. Numbers from the early 1940s run mostly from about 1 million to 5.6 million.
Look for it on naturalization index cards from about 1942 on, or in family papers. Do not add an A to other numbers, such as those on passenger lists; derivative citizenship files also use an A prefix but belong to a different series.
As seen in a recordCourt naturalization index card, 1940s
Vincenzo Russo, naturalized 1944, U.S. District Court, Newark, N.J. A-2814736
Sources
How to cite this page
Daily Ancestor. "A-number." Dictionary of Old Record Words. https://dailyancestor.com/dictionary/immigration/a-number. Last checked 2026-10-03.