Christian Arneson, Milla A. Jacobson from Norway

Christian Arneson (b. May 3, 1874) and his wife Milla A. Jacobson (b. Oct. 24, 1879-1882), arrived in USA from Norway in 1915 with 4 children, Arthur J. Arneson (b. Jul. 29, 1904), Olaf Arneson (b. 1907), Anna Arneson (b. 1909), & Oscar Arneson (b. 1914). Christian is my husband's grandfather and we are trying to locate their town of origin in Norway, or any info on other family members who might have come with them to America. They settled in Great Falls, Cascade Co., Montana upon their arrival. If at all possible, I would like to find out who the parents are, too. My husband thinks they might have come from Oslo but doesn't really know for sure. I would greatly appreciate any help, thank you.