Christian Knutson family

I am trying to get information about my great grandfather and his family. The following is the information I have: Christian Knutson: b. 8/1843 in Norway (not sure where) and died in 1913 in the USA. Served in the US Union army during the Civil War, then returned to Norway to marry and have a family. Immigrated to USA in 1886. Wife: Jeanette C Holm Knutson, b. 9/23/1848 in Norway, died 5/1925 in Minnesota. Children: Elmer Burke Knutson: b. 5/20/1879 in Skien, Norway, d. 1948 Harold Richard Holm Knutson: b. 10/20/1880 in Skien, Norway, d. 8/21/1953 (he was a congressman from Minnesota for 32 years) Dagny (or Dagney) Knutson Bredesen. b. 8/17/85 in Skien, Norway, d. 1/13/1960 in Wisconsin George Elnar Knutson, b. 2/7/1886 in Skien, Norway, d. 12/22/1970 in Long Beach, CA (my grandfather) There was also a son James who was also born in Norway and died in infancy prior to the family's immigration. Family legand is a distant relationship to Roald Amundsen, but I doubt it. Also, perhaps the spelling of the family name was changed upon immigration. I know most of the family tree from immigration on, but nothing from Norway.