The Sumner Heights and Hazelwood Valley Railroad was built as an experimental minimum-gauge railway near Boston in 1875.

[1] The line started from the summit of a small hill just back of the Hazelwood station, on the Providence Railroad, and after winding round the hill by sharp curves, came down through Mr. Mansfield's back yard, and shot by an apparently very dangerous curve obliquely across a street, closely shaving a street corner, where it ran over a small bridge, and then across another street to the side near the railroad, and thence for a short distance parallel with the latter.

It had one 60-foot-long (18 m) bridge, two level road crossings, one reverse curve as well as a switch, turnout and branch.

[1] It would seem, at first sight, that the whole affair was a mere boy’s plaything, and a dangerous one at that; but a test of its capacity undeceived the proprietor of such hasty judgment.

It would appear, to begin with, that the wheels of the car, with their small flanges, would be sure to jump the track at every curve, but by a peculiarity in the way of connecting them with the car (an invention of Mr. Mansfield) they follow the track in every wind and curve as surely as if they were much larger in diameter and had a corresponding depth of flange.