The recently released book Terminal Town has an number of short articles on South Loop historic sites connected with the transportation terminals in the metropolitan region. One of particular interest is the building Trader Joe's is currently in.
From 1928 to 1953 it was the primary bus terminal for intercity buses in the city. It had 300 trips daily in the 1940's from that building. Yes, that way too many for that small of a building. Other bus terminals, particularly the former Greyhound terminal at Clark and Randolph replaced it.