Diane:
I think I may have given you the wrong Eheman for the Scott Co., IA naturalization record I came across at familysearch.org. It was actually a John Jacob "Hamann" who was naturalized at Davenport, IA in 1872. I don't think it's any relation if the surname spelling is any indication. I did find that Augusta Eheman Helmlinger was born in Saxony, Germany abt 1838 - according to the Auglaize Co., OH Federal Census in 1870. Her spouse was a Christian Helmlinger who apparently was a native Ohioan. Sorry to have misled you on the Iowa name. Bruce.