I was just contacted by another person researching the Maders from Friedrichstadt and I may have the connection now.
John Mader & wife came to the US in the 1860's with 4 of his 5 children.One of those children was Adolph, who married a Dorothea.Adolph and Dorothea had 5 children, one of whom was Louis.Could you check to see if this is your Louis?
The John mader who came over was the younger brother of my husband's gr. gr. grandfather.