"No I haven't, as I live in WA state. I heard before 1922, that there were no requirements to be Naturalized. I don't know for sure."
My ancestor Thos. Rebholz probably heard that too because he didn't complete the naturalization process after arriving in 1856, although he did fill out a "Declaration of Intent" form. But his son Andrew, who was 6 mo old in 1856, did have to complete the process to keep his civil service job as a fireman. He filled out 3 Declaration forms from the 1880s-c. 1910 which stale-dated until he finally completed the paperwork for citizenship prior to retiring.
So you should consider posting a request for a look-up in Declaration of Intent indeces at Milwaukee County Historical Society (be sure to include that important death date). The information on those forms is basic: Country of emigration, port of entry & date; hopefully an authentic signature (not the clerk's).
Other places that immigration hints may be found are family newspaper clippings, sometimes including those of the next generation.
"Milwaukee's German Newspapers; an index of death notices and related items" (1844-1950).
Gary Rebholz, compiler/editor