The Yellowstone is the last free flowing river in the lower 48 states. From its headwaters in Lake Yellowstone downstream 670 miles to the Missouri River in North Dakota, the Yellowstone River flows as it has for centuries, in its natural state, undamed and untamed. Clear, cool swift and challenging it offers fishermen and river runners some of the best water Montana has to offer. To fishermen, its blue ribbon waters are known world round for an abundance of big trout. As it flows through Montana the big river goes through many changes - from steep-walled canyons where boulders churn its green waters to the eastern part of the state where the river broadens to take a lazy path through fertile farm country.