John Michaelson (finding a Norwegian)

My ggg - grandfather was John Michaelson. He married Sarah Jane Lawyer in Sangamon Co., Illinois in 1865. He then divorced her in 1878. (same county) They had one son that I know of, my ancestor, John Marion Michaelson. He was from Norway per family. I have checked censuses, land records, naturalization and immigration records. I can not find any information prior or after the marrige. Does anyone have a suggestion?