[samjjones]

Langrish was a real theater owner, and was reportedly one of Swearengen's few friends. I think his purpose is to show that the camp is trying to "mature" into a real town by introducing the arts (in addition to the paper and the school, which are also recurring themes), as well as serving as a fulcrum between the Swearengen and Hearst interests.

But the main reason is that Brian Cox is an effing fantastic actor, and is watchable in whatever he does.