Alright, I have a question that was nagging me for a couple days. I remember reading a trilogy of books (I think there are more, but I didn't read them) about a large number of peoples throughout history taken to an alternate universe, where people were "herded" by some sort of other species (I think their name started with an M).

The most recent group to be taken were from the Civil War age, and they began to rebel against the oppressors.

Can anybody tell me the name of this series?