Good morning Andreas, I was able to find a small obit for John. Not much info though. He died May 12, 1895, per obit. I couldn't find a death record. Wisconsin didn't require a civil death record until 1907. His wife died circa February 18, 1911 in Chicago, per her obit. I couldn't find her in the Illinois death index online, but it is not complete yet. She is buried in Riverside cemetery in Oshkosh. John is most likely buried there too. Her children are mentioned in the obit. Hope this helps. Ruth Pokorny.
The Daily Northwestern (Oshkosh, Wisconsin), Monday, May 13, 1895, page 8, Column 2
John F. Waag of 207 Scott street died Sunday morning and funeral services will be held from St. Peter's church at 9 a.m. on Thursday. He left a widow and five daughters.
The Daily Northwestern (Oshkosh, Wisconsin), Saturday evening, February 18, 1911, Column 4
WAAG--Mrs. John Waag, long a resident of this city, died at Chicago. Her funeral will be held from St. Peter's church Monday morning. The remains arriving in this city Sunday evening. Mrs. Waag was the mother of the late John Waag, Mollie E. Waag, Margaret I. Waag, Mrs. Norn Johnston, Mrs. Louise Stalba, and Tessa McAteer
The Daily Northwestern (Oshkosh, Wisconsin), Monday evening, February 20, 1911, Column 4
WAAG--The remains of Mrs. John Waag arrived over the Chicago & Northwestern railroad at 7:52 o'clock Sunday evening from Chicago, where death occurred. The remains were taken to the undertaking establishment of Spikes & McDonald. Funeral services were held at 9 o'clock this morning at St. Peter's church with Father Clifford officiating. Interment was at Riverside cemetery. Miss Mollie E. Waag, Miss Margaret I. Waag, Mr. and Mrs. Johnston, Mr. and Mrs. Joseph Stalba and Mr. and Mrs. McAteer accompanied the body to this city. The remains were placed in the city vault at Riverside cemetery where they will remain until spring when they will be placed in an underground vault.