The Milwaukee Road electrified portions of its western extension because electric operation could reduce the high cost of oil-fired steam locomotives, perform more efficiently in cold northwest winters, and eliminate dangerous smoke and gas in tunnels, while also benefiting some influential board members with interests in copper and electrical power. In 1912, the company signed power contracts to electrify the line from Harlowton, Montana to Avery, Idaho, and when that section became operational in 1917, the results impressed the board enough to launch a second phase from Othello to Tacoma, Washington. When the second phase was completed in 1920, the Milwaukee had 647 miles of electrified mainline railway, the longest such stretches in the world, and people came from around the world to see the modern marvel. The General Electric EF-1 two-unit locomotives became the tireless workhorses of the electric fleet; nicknamed Pelicans, Black Cows, Mules, and most commonly Box Cabs, forty-two were purchased in 1915 and 1916. General Electric delivered the first two-unit set, numbered 10200, in November 1915, and the Milwaukee Road retired it in August 1973; it is now displayed at the Lake Superior Transportation Museum in Duluth, Minnesota. The original EF-1 Box Cabs easily handled the typical freight trains of the teens, but as longer and heavier freights arrived in the 1930s, the Milwaukee re-arranged the original two-unit locomotives into three-unit EF-2 and EF-3 sets that could haul 30 percent more tonnage, and in the 1950s upgraded the Box Cabs again into four-unit EF-5s that compared favorably to new diesel locomotives.