Dear Ms. Creaney,
Thank you for posting your request on History Hub!
Beginning on September 27, 1906, the responsibility for naturalization proceedings was transferred to the Federal courts. 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 since September 27, 1906 and may be requested through the USCIS Genealogy Program. Please consult USCIS Genealogy Frequently Asked Questions for more information about the process.
We hope this is helpful. Best of luck with your family research!