You have names and dates, but without any context, it's hard to go any further.
Region is very important. Religion is too.
What city, and state, did these great- and great-great grandparents live in?
Do you have reason to believe that the great-greats were born in Germany?Or was it the next generation or so back before that?Where did they settle in the U.S.?
Were they Catholic?If so, they may be from the same region just a little north of Osnabrück, Germany, that the Bornhorst's I'm descended from called home.If they were Protestant, they may be from another area of Germany.