The Jefferson River is a tributary of the Missouri River, approximately 83 miles (134 km) long, in the U.S. state of Montana. The Jefferson River and the Madison River form the official beginning of the Missouri at Missouri Headwaters State Park near Three Forks. It is joined 0.6 miles (1.0 km) downstream (northeast) by the Gallatin.
From broad valleys to a narrow canyon, the Jefferson River passes through a region of significant geological diversity, with some of the oldest and youngest rocks of North America and a diversity of igneous, metamorphic, and sedimentary formations.
The region ...
Click any point for details. Sections without stored geometry are drawn as straight put-in → take-out lines — actual courses follow the river.