Multimodalways has a Freight Service Guide map from 1976.
Nmro.org has a freight schedule from 1956 available for purchase.
Archive.org has an undated freight schedule. Many of the officials are the same as the 1956 freight schedule from nmro.org, so it would be roughly from that era. Researching the dates the various officials held their listed positions could probably narrow the date down further.
Google has a 1922 Freight Shippers Guide available online.