Jammer's of Michigan, I know very little as this is my husbands family. But I did find on the 1930 census the following:
Fred and Matilda Jammer born in Germany, living in Beaver Township Bay County Michigan.
Son Herman Jammer, later married Loucile Zielke; They have 7 children all living in MI. (this is my line)
daughter Anna Jammer.
I hope this helps.