Well, I did find a WWI Draft Registration Card for Martin Davidson, husband to Signe.
His permanent home address is listed as 615 Virginia Avenue, S. Virginia, St. Louis, Missouri. I am from close to St. Louis and am not familiar with a town or city by the name of S. Virginia, but things change.
DOB is listed as July 19 1876.
I am still unable to locate a marriage record, though.