This may be a stretch but I have a William Ernst, born in Germany in 1831.Came to the US in 1857.Married Minnie (Wilhelmina)around 1865.She came from Germany in 1858. His grandson Louis is 93 years old and said William enlisted in the infantry to be become a naturalized citizen after arriving in the US. William settled by Iowa City sometime between 1865 & 1880. I'm not sure where he was between 1857 & 1880.He had 3 children; Lena, Mary & Jerome.Jerome had 4 boys; Carl, Louis, Myron & Warren. William is buried in Fairview Cemetery near Iowa City.Buried next to him is his father John Ernst, born about 1805, died in 1890 at the age of 85 years.Louis said John did not bring a wife with him when he came from Germany - not sure if he was widowed or divorced. Other than the dates fitting your time frame and the familiar names of William, Carl, & Louis, (as family members tend to use the same names) I don't have anything to tie them to your family.