The Lines West electrification had to be beefed - up to handle the higher tractive output ( and therefore higher voltage INput ) of the Little Joes. It was felt that, despite the steeper grades on the Rocky Mountain segment, the Joes would be a better fit on the Montana / Idaho segment, which did have a longer total run and more flatland running. The Joes never ran on the Coast Division Electrification in regular service; only motor # E70, wearing its' as - built number GE-750, tested on the Coast Division.
Among the half - dozen Milwaukee Road Lines West books in my collection, there are several I recommend for a more complete understanding : The Milwaukee Electrics by Noel T. Holley, The Electric Way Across the Mountains by Richard Steinheimer, & Under Milwaukee Wires - featuring the Color Photography of Sanford Goodrick & William C. Janssen, by Bill Marvel.