Big Muddy Creek (Missouri River tributary) Big Muddy Creek (Missouri River tributary) Big Muddy Creek is a tributary of the Missouri River, approximately 191 mi (307 km) long, in the Canadian province of Saskatchewan and the U.S. state of Montana. It flows through the Big Muddy Badlands. It rises in southern Saskatchewan at Willow Bunch Lake, on the plains north of the international border and approximately 20 mi (32 km) northwest of Big Beaver. It flows southeast through the Big Muddy Badlands and through Big Muddy Lake, then south into Sheridan County, Montana, past Redstone, then east, past Plentywood, then south, forming the eastern border of
Muddy River (Nevada) to the Colorado River and followed it westward. In 1844, the expedition of John C. Frémont discovered a cutoff route that avoided the Colorado River, following a route between Resting Springs in California, and the Virgin River Valley that passed through Las Vegas Springs and crossed the Muddy River near modern Glendale. Mormon pioneers blazed a wagon road from Salt Lake City to Los Angeles along this pack trail in 1847, followed by Forty-niners attempting avoid the winter snows of the Sierra Nevada Mountains, and wagon trains of Mormon colonists on their way to settle in San Bernardino in 1852.