Rostock

Hello Listers,
I learned that my ggfather was not with his family in Leussow during the 1867 census, but it said he was in Rostock. He is said to have emigrated to the US in 1868 and wonder if he might have departed from Rostock. Was it a port of departure at that time? I'd like to know where he left from.

Thanks for your help.
Grace Keir in Minnesota USA