1915 Chicago City Directory page 422 from Footnote.com contains the entry for Louis DeMar at 50 West 120th.
His son-in-law, William Apgar is listed in the 1915 directory as well at 10057 S State Street in Chicago--this was also on the Footnote.com site.
I'm working on putting these locations in Google Maps and adding these locations to other known residences of the family.
