I have been working on my family tree and I do have a Joseph Scherr who married a Joanna Josephine Shea. They had three children that I know of -
George Scherr (1886-1968)
Mary A Scherr (1887 - ?)
William Joseph Scherr (1889-1960)
Could the Mary A Scherr that I have be your Margaret Scherr?