The short-lived line was noteworthy in that it was the last common carrier narrow gauge railroad to be constructed in the United States.
Allen was the president of the Boston-Montana Mining Company, which was developing a large silver-mining operation in the remote Pioneer Mountains of far southwestern Montana.
Because of the site's remoteness and poor access, a railroad was considered to be a necessary component of the mining district's development.
From there, the railroad headed south into the Pioneer Mountains, terminating at the booming mining camp of Coolidge, where the Boston-Montana had constructed a 750-ton per day oil flotation mill[1] and other developments.
The steam locomotives and rolling stock used on the line were acquired second-hand from the Florence and Cripple Creek Railroad in Colorado, which had recently been abandoned.