"The Whistling Well" is one of his best stories. I'm told he got the idea for the story when he saw a well in a field and thought "Suppose that whistled. It might if the wind came into it in a certain way."
Actually, the way Cliff told it, his grandfather created the whistling well. His farm was high on a ridge above the Wisconsin River, and while there wasn't really a shortage of water (this was late 19th c., and Cliff's grandfather, Edward "Ned" Wiseman, was a Civil War vet known for stubbornness and cantankerousness...), he wanted a well just in case.
As Cliff portrayed it, the local well drillers told his grandfather it would be pretty expensive to do that, because, as high on the ridge as the farm was, it was a long way down to the water table. But he insisted, so they did it.
Cliff's theory was that on the way down, the drill likely passed through one or more caves, or at least some sort of opening that was connected to the open air, lower in the river valley -- there were a lot of caves all along the ridge on the side where the Wisconsin River lay far below -- so that when the wind was right, it set up a sort of whistling effect, rather like a flute...
Cliff heard that all through his boyhood (his father's farm was right next to his grandfather's place), and never forgot it.
I actually found the well, one of the times when I went down there. But it was badly out of repair, and unused. (No whistles; my guess is that a cave-in, or simply an accumulation of debris falling into the well-shaft, might have blocked it.)