Lightest rail used in wheat country?

[blownout cylinder]

I'm examining some old photos we picked up at a flea market not too far away from where we live. On the back of one of these pix is a comment about a track near an undecipherable location in southern Saskatchewan being at least "40lb". If that is so would that limit you to a RS1? Or what else could have run on this weed infested track?

[cv_acr]

Canadian Pacific had RS23s which were specifically built for light duty branchlines. An RS1/2/3 or SW1200RS would probably also be appropriate.

CN's unique GMD1s were also built specifically for light branchlines. Many prairie lines were restricted for anything heavier. The old National Transcontinental Ry line (one of the forerunners of CN) from Nakina to Cochrane (through Hearst and Kapuskasing - now partially abandoned with the rest operated by Ontario Northland) was the exclusive domain of CN SW1200RS units in the 1970s and '80s.

Light prairie branchlines is the reason 40' boxcars lasted so long (into the early 1990s) in grain service in Canada. It's also the reason CN and the Canadian Wheat Board purchased a number of cylindrical hoppers built from lightweight aluminum instead of steel. (The silver and yellow ones, which are currently being completely eliminated from the roster and scrapped en masse in Thunder Bay)

[wjstix]

The Milwaukee Road had some former narrow gauge lines in southern Minnesota that were restricted to light engines, usually SW-1s. I've pics of a train with like 4 SW-1s on the point pulling a train of 40' boxcars.