Seeking Emmigration Info-What ship?

I am seeking help to find out what ship and what route it took for Ole Olson Espeseth, wife Gjertrud Arnesdatter Espeseth and children came to America. The history of Etenedal state"Ole Olsson and Gjertrud Arnesdatter from Berge in Graneisbygden were among the people from Etnedal that emigrated to America early. That happened about 1850." I do not know the year, but they settled in WI in the middle 1950's.