Have you collected the family death notices for your Matthaeus Berger? They were published in two (2) of Milwaukee's German language newspapers. There were also notices published in these papers for a Mattäus Berger in 1880, son of Matt. and Kath. Berger.
These are indexed in the collection: "Milwaukee's German Newspapers; an index of death notices and related items", covering 1844-1950. There over 150 Berger entries in the index, including several different entries for a Katharine Berger, one referencing Franz Xaver (1895) found in 2 other local German language papers.
Gary Rebholz, compiler/editor
Indexing Milwaukee's German newspapers continuously since 2007... helping to access our historic German-American culture.