i just saw your post. I am also looking for George Frederick jahn. Born about 1851 and died in 1915 San francisco. He was my g grandmothers father. Married to Theresa meinberger. Daughter Edith Louise , george Frederick jahn and 3 other daughters.
they may be the same person. I can't find who his parents are but believe he was born in Prussia You can contact me at firstname.lastname@example.org if you get this message.