Thank you once again Brian for your helpful insights. I agree that I need to let 1868 go as a firm birth date. I guess when there is a headstone that says 1868 and there is paper documentation from a son that states 1868, you start to think it's an absolute fact.
However, when he can't be found in 1868, it makes sense to look elsewhere.
I'll start expanding my search. I'm also going to try to get his obituary from NAHA at St. Olaf College in Northfield, MN throuth the Rowberg files.
The search continues...