In your message you said Bernard Niebuhr came to this country in mid 1800's, WI to IA. I am looking for a Niebuhr who married Sophie Bence, probably in Wisconsin. I suspect Sophie and her husband moved to IA later, as several of her siblings are found there. Sophie was born c. 1839, either Washington or Waukesha Co, WI - probably the latter. She is mentioned in her father's will in 1882, but no mention of where she lived at that time. I cannot tell if the spelling is ie or ei, and suspect they didn't know either! Her sister settled in Waterloo, IA (Black Hawk Co.) My family had a tendancy to go placed in two's and three's, that is why I suspect Sophie was in Iowa by 1870. There is a Peter Neibuhr on the 1870 census, same county as the sister.
Do you know what counties in IA and WI your Bernard is connected to?