Johann Christian Maerz b. Selb, Bavaria, in 1850
A note in Johann Christian Maerz's birth record in Selb, Bavaria, says that he left for America. I do not know if Johann is the same person as John Maerz in the 1880 census in Perham, Otter Tail County, Minnesota, but the census did have John at age 30 and born in Bavaria. I am not related but can connect you with the person who found the record in Bavaria.