Solems in Norway

I have hit a brick wall trying to find out origin of my great-grandparents, Isaac Jacob Solem, b. 1843, and Johanna Magrethe Andersen, b. 1844. It's possible that Johanna came from the Skofteby, Tune, Ostfold area. It's also possible that her parents were Anders Olsen and Elen Brynildsdr, but not proven. I have absolutely no other information on Isaac, except that they showed up in Chicago Census in 1873. My grandmother claimed that Isak Jakob was Jewish. Any help would be appreciated. Please respond to my e-mail address. [email hidden]