The Union Pacific double track Chicago Sub hosts UP's main route from Chicago to Texas and CSX's route south out of Chicago. The Chicago Sub is former C&EI (later MoPac) territory and CSX has had trackage rights for a long time. CSX trains from off the Belt Railway of Chicago and their Barr Yard funnel here. UP operations generally originate or end at Yard Center, The Belt or Proviso Yard.

This is a high traffic route with CSX having the majority of trains during the day while UP dominates in the nighttime hours. Shot shortly after the big mergers of the 1990s, we still see a lot of old paint schemes. Besides UP and CSX we see the EJ&E and Toledo, Peoria and Western at busy crossings on the Chicago Sub.