The Boulder River is a 77-mile tributary of the Jefferson River in southwestern Montana in the United States.
Section of the upper Boulder River
Jefferson River
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The Jefferson River is a tributary of the Missouri River, approximately 83 miles long, in the U.S. state of Montana. The Jefferson River and the Madison River form the official beginning of the Missou
Boulder River (southwestern Montana)
…The Boulder River is a 77-mile (124 km) tributary of the Jefferson River in southwestern Montana in the United States. It rises in the Rocky Mountains at the continental divide in the Beaverhead-Deerlodge National Forest in…
Confluence of Beaverhead and Big Hole Rivers forming the Jefferson near Twin Bridges, Montana
Jefferson River near Parrot Castle, October 2007
Small marine fossils can be found in the Madison Group limestone that makes up the steep, narrow section of the Jefferson River canyon.
Lewis and Clark ascended the Jefferson River in 1805 in their search for a navigable water route to the Pacific.