I am searching for my 2 Great Grandfathers death date? His name is James Frantz, born about 1825, Mecklenburg, Germany. Do not no when he emigrated to the States. He settle in Dane county Wisconsin, until his death. His youngest daughter was born About 1871, so I am assuming that he died between 1872-1879, if he died in 1880 he would of been in the 1880 Census. His family moved to Nebraska. They were in the 1880 Census.
The 1870 census shows James with his wife and family but also living with them is a Fred France [sic] age 47 also born Mecklenburg. He is no doubt your James' brother so you may be able to find them arriving in the USA. Since their daughter Lucy was born circa 1856 in Wisconsin, they must have been in the country in the 1860 census at least. Yep, there he is, living in Middleton Dane Wisconsin in 1860.
Have you tried Vital Records records available for free on Wisconsin Historical Society Site ? They have a death index for Wisconsin pre 1907.
There is also the possiblity that he moved to Nebraska with his family and died there before 1880 census