Just found an obituary stating that one of Marks/Max Welter's daughters was born in Eastern France. Not the greatest news, but at least it takes away the ambiguity of Luxembourg and Germany as other birthplace possibilities.

Where should I start my search? I've never done French research. Here are the details:

Marks/Max Welter b. about 1800
Clara Schulte Welter b. about 1812
children born overseas:
Anna Cora Welter b. 1835
Marie Welter b. about 1837
Regina Welter b. 1838
John Welter b. 1845

They settled in Menominee, Jo Daviess county, Illinois between 1845-1847. More children were born there.

Any help appreciated.