Thank you for posting your question on History Hub.
The National Archives is the repository for the permanently valuable non-current records of the Federal Government. Although only 1-3% of the records created by the Federal Government are transferred to the National Archives, our holdings consist of hundreds of thousands of records, many of which may be of genealogical value. The vast majority of our records are not name-searchable. You will need to begin your research by determining the agency with which your subject interacted and exactly what types of records you wish to see.
For more information on conducting genealogical research within our records, please visit our webpage: https://www.archives.gov/research/genealogy.
If you know which state through which your ancestor came into the United States, you may wish to search for the passenger arrival list for both names for your ancestor. The National Archives has immigration records for arrivals to the United States from foreign ports between approximately 1820 and December 1982 (with gaps). The records are arranged by port or airport of arrival. You will need to contact the regional facility that maintains the records of the state you believe he arrived through. Please consult our website for more information on which National Archives facility to contact: https://www.archives.gov/research/court-records
If you have not already done so, you may also wish to request the vital records of your ancestors to see what names are listed. The Federal government does not ordinarily create or maintain birth, death, marriage, divorce, adoption, or burial records. Such records are made and kept by state and local governments rather than the National Archives. For information on these records, contact the appropriate state, territory, or local bureau of vital statistics.
To locate the state or territory office to contact regarding vital records, please visit: http://www.cdc.gov/nchs/w2w.htm
We hope this information is helpful in your research.
The National Archives and Records Administration