"MAAS, KAU, BAUMGARTNER in Milwaukee Co., WI"
Yes, those names were/are found in Milwaukee Co. A current count of entries from "Milwaukee's German Newspapers; an index of death notices and related items" (1844-1950) includes:
Maas = 300 +/-
Kau (+ Kay) = 50 +/-
Baumgartner / Baumgaertner / Baumgärtner = 130 +/-
(but no "Baumgarter" entries)
Gary Rebholz, compiler/editor
Indexing Milwaukee's German newspapers continuously since 2007... helping to access our historic German-American culture.