Hi Shirley, I haven't done much on this family in awhile and it isn't a direct line for me. This is my son-in-law's family. I've been conferring with another family member. I'll share what I know so far. I don't believe I searched for a marriage record for Isaac and Rebecca. I don't know if there is one. I deduced the approximate marriage date from using census records. The way I connected Isaac to Rebecca (if I remember correctly*) is through a death certificate of Sarah Elizabeth Allen. However, the informant for the death certificate of Oscar G. Allen says his parents were G. W. Allen & Rebecca Jordan. Let me get in touch with my fellow researcher to see if he has come up with anything new.
Marilyn *I'll dig out the death certificate and take a look at it again to confirm.