Musselshell River

The Musselshell River is a tributary of the Missouri River, 341.9 miles long from its origins at the confluence of its North and South Forks near Martinsdale, Montana to its mouth on the Missouri River. It is located east of the Continental divide entirely within Montana in the United States. Counting its pre-confluence tributaries, it measures 425–500 miles in length.
It rises in several forks in the Crazy, Little Belt, and Castle mountains in central Montana. The main branch is formed by the confluence of the North Fork and South Fork in Meagher County, about 25 miles east of White Sulphur Springs, Montana, just east of Martinsdale, north of Martinsdale Reservoir, and just west of Meagher County's border with Wheatland County. The North Fork flows south from the Little Belt Mountains through Bair Reservoir, then southeast. The South Fork flows northeast from the Crazy Mountains. From the confluence of these two waterways, the main branch flows roughly due east past Two Dot, Harlowton, and Roundup, then turns north just past Melstone, and continues to the UL Bend on the Missouri River at the beginning of Fort Peck Reservoir.

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