At one time the original NWP was a busy Class I railroad in its own right, even though for most of its life it was a wholly owned subsidiary of the Southern Pacific.  The lumber industry around Eureka produced long trains of outbound lumber, and numerous industries along the line produced additional inbound and outbound traffic.    At first the traffic justified the high maintenance costs associated with the treacherous geology of the Russian and Eel river canyons, but by the 1970's the line was a money looser.  It eventually morphed into a number of short lines and finally a publicly owned transit agency.  So it is included here under shortlines.

The traditional name Northwestern Pacific has been applied to at least three separate companies.  The original Northwestern Pacific Railroad initially was jointly owned by Santa Fe and SP.  It later became a  wholly owned subsidiary of Southern Pacific, and lasted until the south end of the line was sold to public agencies about 1993.  The new owners created a second incarnation of NWPwhich lasted until 1998.  Following closure of the line by the FRA and subsequent repairs,  a third Northwestern Pacific Railroad took over freight operations between Schellville and Windsor and continues as of this writing, while SMART owns the tracks and runs its passenger service.  The tracks north of Windsor have never been abandoned but remain unused and mostly unloved, waiting for somebody to decide their fate.