John Ahlf can be found for the first time in the 1880 census with his wife, Emma. They lived in Le Sueur, the city. They were both from Hanover, Germany. The "History of the Minnesota Valley Including the Explorers and Pioneers of Minnesota" by Rev. Edward D. Neill (1882) says this on page 484:

"John Ahlf, a native of Germany, was born in 1848. On coming to America he landed first in New York, then went to Le Sueur, where for five years he worked on a railroad. He is now engaged in the liquor trade in Le Sueur. Miss Emma Welter became his wife in 1879 (and from previous page, when he opened his saloon, so emigrated around 1874?). They are the parents of one son, John."

The Termaths are in Le Sueur in the 1880 Census under mother "Hannah" who was born in "Maglinberg" in about 1838 and apparently the dead(?) father was from there too. Oldest son (21 in 1880) "Henry" was born in 1858 in Minnesota and worked as a carpenter. Next oldest brother (17) "John" worked in a butcher shop. There's an Elshoff & Company furniture store which was established in 1871 and the Le Sueur History says about them, "They manufacture a portion of their goods, giving employment to five men" -- maybe Henry was one :-)