Nyhus

I am working on a heritage project for my University, and looking into my mothers side. The entire family has had trouble finding any information past the fourth generation. I have been using ancestry.com and other resources and I do not know what other resources I should be using. Martin Nyhuse born 1865 in Norway is where the information stops. Martin is the person that traveled to America where our family is now but no one can find any information past him. I know he married a woman also from Norway that he met in Minnesota. The spellings keep changing from Nyhuse to Nyhus when looking for this information. Any advice would be appreciated. Thanks!