The beaver slide I have in mind was once used to stack hay all over the West. It was patented as the Beaver County Slide Stacker in the early 1900s. Invented in the Big Hole Valley in Montana, it’s a somewhat portable device, made of wood, that lets someone with a team of horses pull a big wad of hay up the slide and topple it off onto a stack. Before bailing became the thing to do, loose hay in stacks was a way to store and preserve it. Hay stacked that way can last a couple of years—maybe as many as six years, if conditions are right.
The name was popularly shortened to beaver slide by those who used it. Nowadays you’re more likely to see a roll of hay the size of a Volkswagen than a beaver slide and a loose stack. However, the University of Montana notes that a few ranchers are going back to this method because it saves money and fuel.
The beaver slide in the picture was being run by Nona Virgin on the Railroad Ranch in the Island Park country, probably in the 1920s.