After the Coast Division was electrified via the Cascades, the Milwaukee Road procured very large passenger locomotives for the increasingly heavy trains. Due to the allocation to the manufacturers ordered by the US Railroad Administration, a further ten EP-3s from Baldwin-Westinghouse were built in parallel to the five EP-2s from General Electric. Although the EP-3 was heavier, it appeared more graceful in general.

Railway and Locomotive Engineering, April 1918

The locomotive body was not divided here, which made greater demands on the division of the chassis. In principle, the locomotives each consisted of two chassis groups, each of which resembled a Pacific steam locomotive and were coupled to one another. Each axle was driven by a double motor, which was mounted in the frame and was therefore not part of the unsprung mass. The drive was here via hollow shafts, which gave the locomotives the nickname “Quills”. Above the coupling between the chassis parts was the oil-fired oven for the train heating,

Sectional drawing with dimensions

Due to the relatively rigid overall construction and the lack of mobility of the axles, the great wear and tear on the wheel flanges soon became apparent during operation, and there were also derailments. In retrospect, the weight-saving design of the locomotives did not prove to be advantageous either, so that the frames broke. Dividing the locomotive body of one of the locomotives into two parts was not expedient and even several modifications to the chassis and other assemblies of the locomotives could not eliminate all problems.

After the Second World War, the EP-4 „Little Joe” took over the duties of the EP-3. While other electric locomotives, badly worn out during the war, had been refurbished, this was not considered useful for the EP-3. Thus, the seven remaining vehicles were all scrapped between 1952 and 1957.