Dear Mr. Anderson,
Thank you for posting your request on History Hub!
To determine the unit to which he was assigned, we suggest that you request a copy of his Official Military Personnel File (OMPF). OMPFs and individual medical reports for enlisted men of the U.S. Army who were separated from the service after October 1912 and prior to 1958 are in the custody of NARA's National Personnel Records Center in St. Louis. In many cases where personnel records were destroyed in the 1973 fire, proof of service can be provided from other records such as morning reports, payrolls, and military orders, and a certificate of military service will be issued. Please complete a GSA Standard Form 180 and mail it to NARA's National Personnel Records Center, (Military Personnel Records), 1 Archives Drive, St. Louis, MO 63138-1002. You also may fax the form to 314-801-9195. For more information see Official Military Personnel Files (OMPF), Archival Records Requests.
Due to the coronavirus public health emergency, the National Personnel Records Center is servicing only urgent requests related to homeless veterans, medical emergencies, and funerals which may be faxed to 314-801-0764. We thank you for your patience and look forward to resuming normal operations when the public health emergency has ended.
We searched the National Archives Catalog and located the series Records of Engineer Regiments and Battalions, 1912-1921 in Records of U.S. Regular Army Mobile Units, 1815-1970 (Record Group 391) that may include records of the 118th Engineer Regiment during WWI. For access to these records, please contact the National Archives at College Park - Textual Reference (RDT2) via email at email@example.com.
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 RDT2. We apologize for this inconvenience and appreciate your understanding and patience.
We hope this is helpful. Best of luck with your family research!