Dear Ms. Forward,
Thanks for posting your request on History Hub!
Witnesses are required to be citizens of the United States either by birth or naturalization. A former alien can serve as a witness if he/she is also a naturalized U.S. citizen. Naturalized citizens who serve as witnesses are required to show proof of their status in the form of a certificate of naturalization.
We hope this is helpful. Best of luck with your research!
[Information provided by Elizabeth Burnes]