Ellef R. Mohn was born in Tyldalen, Norway in 1868. He emigrated to the United States 1891 in order to avoid compulsory draft in Norway. He first settled near Valley City, later moving to Ransom County.
He married Oline Shjerbeck in 1897, and they came to homestead near Ypsilanti, in Stutsman County, North Dakota, in 1899. Born in Minnesota in 1880, Oline had moved with her parents to Fort Ransom, traveling by wagon pulled by oxen.
Ellef and Oline Mohn were the parents of nine children: Rudolph, Minnie, Donald, Elma, Henry, Bessie, Inga, Olaf, and Clara.