Seeking for Bohnsacks Who Came from Germany and Settled IN Iowa

The oldest one we know is Hans BOHNSACK born in 1819 in the Schleswig-Holstein section of Germany, but we know not which city. Herman Frederick BOHNSACK is my grandmother's father, and we know nothing about him except his birthdate(1872)and his wife's name(Mathilda Hannah STUHR) and birthdate(1883). I loved both of these people, but when they died I was too young to care about their histories or origins. Now, when I care passionately, it may be too late. Are these names in your histories? Will you share what you know, please?