Complex sentence: The old MCC, now on the National Register of Historic Places, consisted of two identical control rooms and was replaced in 1997 with a new MCC, which has one large room for Shuttle flights, and a smaller size auditorium for International Space Station operations.
Split into simpler sentences: The old MCC, now on the National Register of Historic Places, consisted of two identical control rooms. It was replaced in 1997 by a new MCC, which has one large room for Shuttle flights, and a smaller auditorium for International Space Station operations.