I have a distant relative, Jeremiah Thompson b abt 1819 in Cumberland PA. He married Louisa and they had a daughter Sarah who became by Grandmother's Grandmother. I understand that Sarah Thompson was a full blooded Seneca.

Any suggestions to guide me in my search for Jeremiah Thompson's ancestors?

Have you found Jeremiah and his family in any census records? That is a good place to start. Also the census records for Sarah after she married into the family. If she lived long enough, she may have listed Jeremiah and her mother's state of birth, etc. Also try church and historical records in there areas where they lived.

Carolyne