sheds. Electric locomotives handled mainline freight and passenger trains on this section exclusively. The route was de-energized and catenary dismantled in 1956, after the Cascade Tunnel was fitted with ventilation fans. Michigan Central Railroad (Detroit Tunnel Lines) The Michigan Central Railroad electrified the tunnels under the Detroit river in 1910. The system used a under-running third rail. The electrification covered a total of between two passenger stations in Detroit and Windsor. The total track mileage covered around , which included not only the station and tunnel lines but also an extensive yard. The electrification was discontinued in the early 1950s when the tunnel was ventilated so that diesels could run through. Mountainous Terrain Butte, Anaconda and Pacific Railway The BA&P, a copper ore-hauling short line in Montana, electrified in 1913 using a system engineered by General Electric. It was the first primarily freight railroad in North America to electrify. Original motive power was in the form of 28 identical B-B boxcabs, which served until de-electrification in 1967, by which time diesel-electric locomotives were cheaper to run. GE used the BA&P as a model railroad for demonstrating the success of its DC electrification techniques. The Milwaukee Road electrified soon afterward using a similar technique at . Chicago, Milwaukee and St. Paul Railroad (the Milwaukee Road) The Chicago, Milwaukee and St. Paul Railroad ('Pacific' was not added to the title until incorporation in 1927) electrified two of its mountainous divisions using a DC overhead system. The two divisions were widely separated from each other, but plans to electrify the intervening , the relatively flat Idaho Division from Avery to Othello, were never implemented. The electrification system was similar to that of the Butte, Anaconda & Pacific, but was at rather than . The higher voltage was chosen because of the load conditions with 2,500 ton trains. Rocky Mountain Division (Harlowton to Avery) The first division to be electrified was the Rocky Mountain Division from Harlowton, Montana to Avery, Idaho. This covered a distance of and began electric operation in 1917. The electrification remained in operation until 1974, when diesel locomotives took over. There were two main reasons for electrifying this division. The first was to get through the Bitter Root Mountains, which are steeply graded. The second was that the line passes through an important forest reserve of the US Government. Steam trains were a fire hazard, and thus electric trains lessened