Coming in late, I see others have picked up the easy ones - the NP's Coeur d' Alene Railway & Navigaton Co, and the GN's Kaslo & Slocan. There are some other oddities in the northwest.
The South Ainsworth - Wallula trackage of the NP was originally constructed to narrow gauge to allow use of the exisiting 36 inch gauge Walla Walla & Columbia River equipment along this section of line, which was vital because low water conditions sometimes hampered sternwheel operation between Wallula and Ainsworth (North bank of the mouth of the Snake River) disrupting the flow of construction supplies for the NP.
The GN acquired and standard gauged the Great Falls & Canada, in Montana.
Charlie Mutschler
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