Lars Knutson and Elizabeth Marie Hansen, IA/NE/MI

I'm looking for information on Lars Knutson (originally Knudsen) and his wife Elizabeth Marie Hansen, who emigrated from Kristiania in 1883 with their children. They lived in Marshalltown, Gilman and South Omaha. Marie died c. 1888, Lars may have died sometime after 1910. Two of their children emigrated to Canada (Axel and Sigurd). I am trying to find more information about the descendents who remained in the U.S. Any information is greatly appreciated. Thomas