Thanks to all so much for responding to my post. I haven't had a chance to match up the different findings-all of which seem promising-but the age cohorts seem right. Perhaps Hattie came to Milwaukee from Michigan for the sole purpose of having the child (as was the practice for unwed mothers at that time I believe)and then returned to Michigan. Looking at the other reasons for giving up a child for adoption at that time, this seems the most logical explanation. I can think of no other reason why a young woman would relinquish her newborn for adoption, unless she and the family were without means to provide support. These clues will all help put the puzzle together.
Thanks again.