The demand for proof of citizenship resulted in the creation of certificates of naturalization during the “Old Law” period of United States naturalization history (March 26, 1790–September 26, 1906). Government efforts to end naturalization fraud and ensure documentation of all naturalized citizens motivated the evolution of certificates throughout the “Certificate File (C-File)” period (September 27, 1906–March 31, 1956).

“Old Law” Period (March 26, 1790–September 26, 1906)

During the “Old Law” period, there was no federal oversight for the issuance of certificates of naturalization. Early naturalization laws allowed any "court of record" (municipal, county, state, or federal) to grant United States citizenship and did not even require courts to issue certificates.

Early certificates did not include important biographical information or security features. Without centralized content control, naturalization records often contained little more than the applicant’s name, the names of witnesses, and the country to which they renounced allegiance. Many courts’ certificates did not include a description of the person naturalized and were consequently easily transferable. The variation and absence of biometric information and security features made authenticating certificates of naturalization difficult, facilitating fraud.

Additionally, many certificates omitted names of family members who derived United States citizenship from the primary subject’s naturalization. 

Courts did not keep copies of “Old Law” certificates of naturalization as insurance against loss of the original certificate by the naturalized citizen and/or destruction of the naturalization court’s records. The lack of provision for backup copies of naturalization records left both citizens and the government vulnerable to regional disasters which destroyed local court records. 

“Certificate File (C-File)” period (September 27, 1906–March 31, 1956)

Congress passed the Basic Naturalization Act of 1906 to correct deficiencies in “Old Law” certificates of naturalization (and many other problems with the early naturalization system).  The law took effect September 27, 1906, founding the federal Naturalization Service, inaugurating the “Certificate File (C-File)” period, and transforming naturalization recordkeeping.

The Basic Naturalization Act of 1906 was Congress’ first real attempt at federal supervision of naturalization. It also marked the first time that the administration of the certificate of naturalization was specified by federal law. Beginning September 27, 1906, federal laws and regulations – enforced by an administrative oversight agency with stringent penalties for violations – required that all naturalization courts nationwide:

  • Issue a certificate of naturalization to every naturalized person (and name all members of the primary subject’s family who derived citizenship from the naturalization);
  • Create certificates of naturalization using standard forms distributed by the Naturalization Service which controlled the content, format, and quality of the records;
  • Submit a duplicate copy of every certificate of naturalization to the Naturalization Service for filing in a C-File; and
  • Only issue replacement or duplicate certificates with approval of the Naturalization Service.

Every person naturalized between September 27, 1906, and March 31, 1956, had a C-File created containing a copy of their certificate of naturalization. 

The Naturalization Service distributed three versions of its standard form certificate of naturalization during the “Certificate File (C-File)” period (1906–1956):

Form 2207 (September 27, 1906–June 30, 1929) 

Form 2207 Certificates of Naturalization issued between September 27, 1906, and June 30, 1929, could include the following 

  • Biographical information about the rightful holder: name of holder; signature of holder; address of holder; country of former citizenship; and physical description of holder: age in years (when naturalized), height in feet and inches, color (race), complexion, eye color, hair color, and visible distinguishing marks. 
  • Biographical Information about the subject’s family: name, age, and place of residence of wife; and names, ages, and places of residence of minor children.
  • Security features: printed on safety paper; certificate number at top on left (C-Number, which corresponds to the Naturalization Service's C-File); certificates were consecutively numbered; and petition volume and number (facilitating location of the petition for naturalization in court records).
  • Court information: state and county of court; date, court, and location of naturalization; court's seal (only on original, not duplicate sent to Naturalization Service); court official's signature attesting to the facts listed on the certificate.

Form 2207 with Photograph (July 1, 1929–January 12, 1941)

The Registry Act of 1929 brought changes to Form 2207 starting July 1, 1929.

Form 2207s issued after July 1, 1929, bear a signed photograph of the rightful holder and show any name change on the certificate.  

The Registry Act of 1929 also authorized the Naturalization Service to begin issuing certificates of citizenship to persons receiving United States citizenship after birth but not receiving certificates of naturalization from a naturalization court (e.g., persons deriving citizenship or repatriating). 

Standard Form N-550 (January 13, 1941–present)

The Naturalization Service united with the Immigration Service to form the Immigration and Naturalization Service (INS) in 1933. The INS transferred from the Department of Labor to the Justice Department in 1940. The Naturalization Service renumbered and reformatted its forms to reflect this restructuring and bring its certificate of naturalization into compliance with the requirements of the Nationality Act of 1940.

INS continued to use Form N-550 with many amendments and new versions issued. Beginning April 1, 1956, creation of C-Files formally ended, and all certificates of naturalization (and all immigration and naturalization records) went into an individual’s Alien File (A-File). This practice continues today. 

Today C-Files are in the custody of the United States Citizenship and Immigration Services (USCIS), and can be requested through the USCIS Genealogy Program.  

In most cases, the National Archives will not have a copy of the certificate of naturalization. Two copies of the certificate were created after September 26, 1906 – one given to the petitioner as proof of citizenship, and one forwarded by the courts to the INS.

Certificates of naturalization were issued by the federal courts until October 1991 when naturalization became an administrative function under the INS.

Learn more about certificates of naturalization: