Christian Johnson Lena Torgerson or Torgersdatter

I am trying to locate ancestors from when they lived in Norway. I have a Christian Johnson b. Feb 1829 d. Apr 30, 1918 immigrated in 1867 from Norway resided in Marshall County Minnesota. First wife Eliza Johnson possibly a Erickson and had 6 children john, anna, erick, charley, sophia, paul all born betwenn 1855-1868. Christians second wife was Lena Torgerson or Torgersdatter Ronningen. Lena was born Oct 1855, d. Sep 24, 1935 they had 9 children. Olaf, Theodore, Charley, Helmer, Juluis, Edwin, Nora, Otto and Clara. Otto and Clara were twins and Clara is my great grandmother. Children were born between years 1877-1896. I'm am having trouble locating them before 1880 and am in need of guidance or direction on where to look for them next. Please email me at [email hidden] with any suggestions.