I saw this late at night on TCM. !!! I spent years hiking down in the Grand Canyon, and this is the real thing. The plot is not important. The footage of the Canyon is not made of Southern California location shots, but spectacular film of various places on the South Rim, and in the side canyons below. I recognize many stretches of the Bright Angel Trail, though how they got a horse to gallop up it, I have no idea. The NPS pack mules slog along slowly, and most humans, myself included, manage only two or three miles and hour, up hill. Watch this movie, if only to see the Grand Canyon as it was before the "improvements" of the 21st century!
