With some cemetery documents, I was able to confirm another branch of Ole and Mari's eldest daughter, Elizabeth. Elizabeth and Ole Andreas Knutson had a daughter, Mary who married Stephen Olson.
In 1900, Mary and husband Stephen lived in Independence township, Palo Alto County, Iowa. Along with her husband, Mary lived with sons Orville, Elmer, Stanley and daughter Marnie.
While errors are common in tracing genealogy, they can be frustrating. Eventually you come to accept them along with the roadblocks.
The 1900 US Federal Census indicates that Mary had 5 children, of which 4 were living in 1900. However, a later census (which I'll be posting later) indicates Mary had 7 children, all of which were living at the time of the census. So it's difficult to determine which census record is correct.