Dear Ms. Ferrari,
Thank you for posting your request on History Hub!
Since some U.S. census records will indicate the year that the person immigrated and/or was naturalized, we suggest reviewing the NARA’s Online Census and Other Resources using the link to the National Archives Catalog. All the U.S. census population schedules are part of the Records of the Bureau of the Census (Record Group 29). Beginning with the 1850 census, each person listed. The information generally includes the person's name, relationship to head of the household, sex, age, marital status, occupation, place of birth, citizenship, and education. Some of these schedules are digitized. To obtain a copy or view the non-digitized records, please contact the National Archives at Washington, DC - Textual Reference (RDT1) via email at firstname.lastname@example.org.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RDT1. We apologize for this inconvenience and appreciate your understanding and patience.
Ancestry has digitized the U.S. census population schedules and they are searchable by name. In response to the COVID-19 pandemic, the National Archives has partnered with Ancestry to make the vast majority of their NARA-digitized holdings freely available to the public. Anyone with Internet access may create an account, access NARA records, and use other Ancestry resources, such as their educational offerings and family tree-maker application. For more information see Ancestry’s announcement -- “Free At-Home Education Resources From Ancestry® and Access to Nearly 500M National Archives Records”.
If your great-grandfather indicated during a census that he is a US Citizen or naturalized, when that occurred will determine where his naturalization records are available. Prior to September 27, 1906, any "court of record" (municipal, county, state, or Federal) could grant United States citizenship. Often petitioners went to the court most geographically convenient for them. As a general rule, the National Archives does not have naturalization records created in state or local courts. However, a few indexes and records have been donated to the National Archives from counties, states, and local courts. Please contact the National Archives facility serving the state in which the petitioner resided to determine if records from lower courts are available. In certain cases, county court naturalization records maintained by the National Archives are available as microfilm publications. Records from state and local courts are often at state archives or county historical societies.
Beginning on September 27, 1906, the responsibility for naturalization proceedings was transferred to the Federal courts. If a naturalization took place in a Federal court, naturalization indexes, declarations of intention (with any accompanying certificates of arrival), and petitions for naturalization will usually be in the custody of the National Archives facility serving the state in which the Federal court is located. Unfortunately, no central index exists. To ensure a successful request with your request, please include the name of petitioner (including known variants); date of birth; approximate date of entry to the US; approximate date of naturalization; where the individual was residing at the time of naturalization (city/county/state); and country of origin.
In most cases, the National Archives will not have a copy of the certificate of citizenship. Two copies of the certificate were created – one given to the petitioner as proof of citizenship, and one forwarded to the Immigration and Naturalization Service (INS). Certificates of citizenship were issued by the Federal courts until October 1991 when INS took over responsibility for naturalization proceedings. All INS records are now overseen by the US Citizenship and Immigration Services (USCIS). USCIS maintains duplicate copies of court records (including the certificate of citizenship) created from September 27, 1906 to March 31, 1956 within Certificate Files (C-Files). Beginning April 1, 1956, INS began filing all naturalization records in a subject’s Alien File (A-File). C-Files and certain A-Files can be requested through the USCIS Genealogy Program.
We hope this is helpful. Best of luck with your family research!