I went back and analyzed the family tree in the Hagerman Valley Family Tree and the father Lewis E. McMahon was born Aug 1857 in Virginia. I don't think that family ever got to Idaho.
Your Lewis/Louis was not married in 1900 but then was divorced on the 1910 Census. I'd check with the Owyhee County Historical Society, visitidaho.org/thingstodo/view-attraction.aspa?id=30780 .
I'd also check with Lincoln County Clerk, 208-886-7641.