East Side of the West Yards, Springfield. JA Jct (Jefferson Ave Jct) is where the Clinton Sub connected with the St Louis line.
Rich nailed it. Assuming that it is lettered for the Frisco - and I can't quite tell for certain - it's either 451 or 452 (renumbered), which were the only two rebuilt troop sleeper "working baggage" cars. See the Forum - Historical - Passenger Cars - Express Cars tree for more on these dandies.
