Why does ORD have two towers? I flew in there for a connecting flight this last weekend and saw two towers standing, one obviously larger than the other.
Simply put, a lot of airports, especially ones that are Class B (very busy), will have multiple control towers. Most of the time, there is a single operational control tower focused on departures/arrivals into the airport environment with one or multiple smaller ground control towers focused on ground movement area coordination. I hope this helps!