BARZ and BARTZ are interchangeable we have discovered in our family line. There are may be other spellings as well. We have a Karl BARZ ( BARTZ ) in Joliet IL, same generation as your Karl, with one adopted daughter. There seems a possibility that some of the family went to MN. We are trying to locate descendants of the five brothers...Albert, Karl, Ernst, August, and Herman, who immigrated about 1881. My ancestor was Ernst. Their parents were Ernst Theodor Erdman BARZ and Caroline Auguste BECKER of German ancestry from Pomerania Prussia ( Poland ).The family was Lutheran.If you think there might be a connection, I can be contacted at email@example.comTricia M.