I have been able to find this information since posting this message:
St. Louis City Death Records, 1850-1908 about Henry Mantz (should be Mentz) Name: Henry Mantz Death Date: 15 Feb 1885 Address: 1829 North Market Volume: 16 Page: 861 County Library: RDSL 25 Missouri Archive: C 10382 SLGS Rolls: 319
Hello Mr. Straub,
Our records indicate that Henry Mentz and Catherine Mentz are both buried on Lot 407 Section 7. Henry is in grave #1 and Catherine is in grave #4.Our records are not online yet, however, we do have links to the cemetery maps.Simply find section 7 on the overall map of St Peter's and then click on the number 7 and it will open a map of the entire section.You need to look at the north half of the Section to locate Lot 407.
Henry Mentz died at the age of 61 and was interred on 2/17/1885 Catherine Mentz died at the age of 78 and was interred on 5/16/1910 There are no stones on the lot.Other family members buried there are as follows:
William Mentz who died at the age of 26 and was interred on 9/16/1891 Julia Mentz a 1 year old, who was interred on 10/8/1896 and Frank H. Mentz, Sr who was 68 year old when he died and he was interred on 9/30/1927
Possible Marrige record as his wife Cathrine Winkelmann came over to the US in 1860 from Siselen, Canton Bern:
St. Louis, Missouri Marriages, 1804-76 about Heinrich Meng Name: Katharine Winkelmann Spouse: Heinrich Meng Marriage Date: 11 Apr 1860 Volume/Page: 10-119