Last verified: September 30, 2026. Official procedures can change; use the linked agency pages when you file.
U.S. naturalization records are not all stored in one place. The court, year and record series determine whether you should be looking at NARA, a state/local repository, or USCIS.
Before September 27, 1906
Naturalization could occur in many federal, state and local courts. There was no single centralized federal record system. Start with the place the person lived and the court or archive that holds that jurisdiction’s records.
September 27, 1906 through March 31, 1956
After federal standardization, duplicate naturalization records went to the immigration service. USCIS says its historical C-Files cover naturalization certificates and related records from September 27, 1906 through March 31, 1956. NARA may separately hold court petitions and declarations from federal courts.
Beginning April 1, 1956
NARA’s current naturalization guidance says INS began filing naturalization records in the subject’s A-File on April 1, 1956. That makes the A-File particularly important for later-1950s and subsequent immigration/naturalization histories.
October 1991 and later
Naturalization became an administrative function under INS rather than the federal courts. NARA says it does not hold U.S. District Court naturalization records created after that transfer.
A practical search order
Build a date-and-place range
Use censuses, directories, family papers, passenger records and genealogy databases to narrow where and when naturalization may have happened.
Search NARA holdings
For federal-court records before October 1991, check the NARA facility serving that court. If it is not in NARA, the court may still retain it.
Check state/local repositories
State and local court naturalizations can be in state archives, county repositories or historical societies.
Use USCIS for the federal immigration file when appropriate
For C-Files, A-Files and later USCIS-controlled records, follow the current Genealogy or FOIA route that matches the record and person.
Related guides
Ancestry & FamilySearch
How we used genealogy databases to narrow names, dates, places and record leads.
Read guide →A-FileUSCIS vs. NARA
Choose the right repository for the federal immigration file.
Read guide →A-numberFind an A-number
Use old correspondence and catalogs to identify the federal file number.
Read guide →Official / primary sources
We separate current source-based guidance from our own family’s experience. Agency custody, forms, fees and procedures can change.