There's actually an excellent book written about the Red Electrics but has been out of print for many years - "The Red Electrics - Southern Pacific's Oregon Interurban".
The system was built in response to the Oregon Electric - originally thought to be nothing more than another failed attempt to build in the Willamette Valley, it was soon discovered that James J. Hill was bankrolling it through his Spokane, Portland & Seattle Railway (50/50 owned by GN and NP). Once Edward Harriman got wind of the arrangement, the SP was not to be outdone.
The equipment was similar to that used by the Pacific Electric but generally shorter in length; as the equipment was compatible most Red Electric equipment ended up on the PE after the Reds stopped running in 1929. Most cars were converted to baggage express. Two pieces of Red Electric equipment remain in existence at the Orange Empire Railroad Museum - a baggage motor, and a rider coach.
There are several Red Electric related structures still in existance to this day - substation structures in Lake Oswego (converted to an apartment), Dundee (in disrepair) and McCoy (in disrepair), stations in Forest Grove (converted to office), McMinnville (still in railroad use), and Corvallis (relocated, now a restaurant); four wig-wag signals (two on the Willamette Shores Trolley line, one former McMinnville wig-wag now at the Oregon Zoo and another at a railroad display in Toledo, near Newport), signal foundations along the WST stretch and on the P&W Tillamook District between Lake Oswego and Cook.
The long term intent was for the Red Electrics to become a valley-wide system, including a mainline that would parallel the "steam mainline" that exists today as Union Pacific's mainline. However, growth never came to be - the Red Electrics were down by 1929 with the OE just a few years later. SP ran steam passenger service or a motorcar on some segments for just a few years before it was all converted to bus service - if anything.
Today the Red Electrics are a mere memory for a few, and forgotten by most. Most of the railroad still exists, the Willamette Shores Trolley gives you a chance to ride a part of it (and the new WES line actually uses a line which was electrified for use by Red Electric trains, but in general was not used by revenue trains...however the Red Electric shop was located along this stretch). The City of Portland is developing a plan for a "Red Electric" trail near Hillsdale on the old right-of-way.
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Erik Halstead - Portland, Oregon