For traffic through the Cascade Tunnel, the Great Northern received four four-axle boxcab electric locomotives in 1909. They were built by ALCO with their electrical equipment supplied by General Electric. Operating under 6,600 V three-phase AC at 25 Hz, each locomotive delivered 1,900 hp for an hour and 1,600 hp continuously. Power was transmitted via two trolley poles and the rails.

The locomotives were only used for the traffic in the tunnel and at both ends, steam locomotives took over. The electrified section through the tunnel was roughly three miles long and had a grade of 1.7 percent. Thanks to their multiple control equipment, three of the locomotives could be used to haul heavy freight trains at 15.7 mph (25.3 km/h). As train weights grew, all four locomotives were used together, but the speed had to be halved to 7.8 mph (12.6 km/h) to reduce the strain on the power supply.