Researching the surname Bohl in the Lake Konstanz area

My great -great grandfather, Marquardt Bohl(born in 1818) left the Baden region in 1854 and settled in Brooklyn, NY. He served in the 52nd regiment NY during the Civil War and I'm pretty sure there was another relative who also served. I have been able to learn that the Bohl's originally came out of Switzerland into the Baden region around the early to mid 1700's. I would like to be able to find out whether I have any living relatives there but am not sure as to how to progress. Any suggestions would be most welcome.