Mikelson- B. 1866 in Norway

My grandmother has no info on her mothers parents except they were both born in Norway. Hogan Mikelson was born on 14 July 1866 came to the US in 1870. He met his wife Bertha Nelson also from Norway in Clarion, Iowa on 20 Feb 1895. Hogan died 18 April 1935 in Clarion, Iowa. Bertha Nelson Mikelson was on 22 Sept 1864 in Norway. She died on 26 March 1945. My grandma remembers meeting Bertha's sister as a child. But, does not recall her name. My grandma is 85 and I would love to find out what I can on her great-grandparents. Thanks in advance!