Sioux Falls, South Dakota.
You must be referring to that hilarious film The Hallelujah Trail, where the wagons loaded with Denver’s winter supply of whiskey were lost in quicksand.
The West was, and is, home to plenty of quicksand locations, formed when mud, sand or even gravel comes in contact with an underground stream or spring. But the truth is that most quicksand is rarely deeper than a few feet. Although I know of a few cases when people, animals, automobiles and even a locomotive were sucked under and vanished without a trace, these were rare occurrences.
Marshall Trimble is Arizona’s official historian. His latest book is Wyatt Earp: Showdown at Tombstone. If you have a question, write: Ask the Marshall, P.O. Box 8008, Cave Creek, AZ 85327 or e-mail him at email@example.com