Historical Records are files, forms, and documents now located within the following records series:

Naturalization Certificate Files (C-Files), from September 27, 1906 to April 1, 1956. Copies of records relating to all U.S. naturalizations in Federal, State, county, or municipal courts, overseas military naturalizations, replacement of old law naturalization certificates, and the issuance of Certificates of Citizenship in derivative, repatriation, and resumption cases. The majority of C-Files exist only on microfilm. Standard C-Files generally contain at least one application form (Declaration of Intention and/or Petition for Naturalization, or other application) and a duplicate certificate of naturalization or certificate of citizenship. Many files contain additional documents, including correspondence, affidavits, or other records. Only C-Files dating from 1929 onward include photographs.

Microfilmed Alien Registration Forms, from August 1, 1940 to March 31, 1944. Microfilmed copies of 5.5 million Alien Registration Forms (Form AR-2) completed by all aliens age 14 and older, residing in or entering the United States between August 1, 1940 and March 31, 1944. The two-page form called for the following information: Name; name at arrival; other names used; street address; post-office address; date of birth; place of birth; citizenship; sex; marital status; race; height; weight; hair and eye color; date, place, vessel, and class of admission of last arrival in United States; date of first arrival in United States; number of years in United States; usual occupation; present occupation; name, address, and business of present employer; membership in clubs, organizations, or societies; dates and nature of military or naval service; whether citizenship papers filed, and if so date, place, and court for declaration or petition; number of relatives living in the United States; arrest record, including date, place, and disposition of each arrest; whether or not affiliated with a foreign government; signature; and fingerprint.

Visa Files, from July 1, 1924 to March 31, 1944. Original arrival records of immigrants admitted for permanent residence under provisions of the Immigration Act of 1924. Visa forms contain all information normally found on a ship passenger list of the period, as well as the immigrant's places of residence for 5 years prior to emigration, names of both the immigrant's parents, and other data. In most cases, birth records or affidavits are attached to the visa, and in some cases, marriage, military, or police records may also be attached to the visa.

Registry Files, from March 2, 1929 to March 31, 1944. Original records documenting the creation of immigrant arrival records for persons who entered the United States prior to July 1, 1924, and for whom no arrival record could later be found. Most files also include documents supporting the immigrant's claims regarding arrival and residence (e.g., proofs of residence, receipts, and employment records).

Alien-Files numbered below 8 million (A8000000), and documents therein dated prior to May 1, 1951. Individual alien case files (A-files) became the official file for all immigration records created or consolidated after April 1, 1944. The United States issued A-numbers ranging up to approximately 6 million to aliens and immigrants who were within or entered the United States between 1940 and 1945. The United States entered the 6 million and 7 million series of A-numbers between circa 1944 and May 1, 1951. Any documents dated after May 1, 1951, though found in an A-File numbered below 8 million, will remain subject to FOIA/PA restrictions.