The connection with the PFW&C was at the south end of the CUS trackage at the Roosevelt Road crossing.
The last Pennsylvania Railroad train into the north side of Union Station (via the PCC&StL) ran April 23, 1927; afterwards, PRR passenger service ran out the south side and the PFW&C, using the South Chicago and Southern Railroad to reach the PCC&StL.
Buildings were gradually built over the sunken approach tracks using leased air rights.
The CM&StP became the Chicago, Milwaukee, St. Paul and Pacific Railroad in 1928.
In May of 2017, the Chicago Union Station company dissolved, with its assets now being owned directly by Amtrak.