American River
The North Fork is the longest tributary of the American River, at . It begins at an elevation of about near Lake Tahoe in Placer County at Mountain Meadow Lake, just northeast of Granite Chief and immediately due west of Squaw Valley Ski Resort. It flows westward through remote wilderness areas.
Locust Fork of the Black Warrior River
History
The Locust Fork is an ancient river with a surprising history. The river and its tributaries have carved a path through the surrounding ridges of sandstone and chert at least a dozen times - geological evidence that this river is older than the hills through which it flows.
That geology demonstrates that across the millennia as the Appalachians and other uplifts of the land slowly took place, the river cut through. Today it exhibits hairpin curves bordered by steep bluffs, called “entrenched meanders”. Together the river and ridges have created an array of habitats for a distinctively rich diversity of life. (Adapted from Jim Lacefield, author of “Lost Worlds in Alabama Rocks”.)
In spite of threats, the Locust Fork remains free-flowing, preserving some of that rich bio-diversity, although human activity has caused many extinctions of rare and unusual species.
The river provided Native Americans ample food and shelter, resulting in abundant artifacts in the watershed. 
The river’s winding course caused the early white settlers to build many bridges, some of which survive from the past: Swann Covered Bridge https://en.wikipedia.org/wiki/Swann_Covered_Bridge Horton Mill Covered Bridge
https://en.wikipedia.org/wiki/Horton_Mill_Covered_Bridge and Easly Covered Bridge
Today just in Blount County 115 bridges longer than 20 feet currently in operation cross the Locust Fork River.
Settlers also built grain mills in almost every valley. Most of them are gone. 
Additional sources:
Friends of the Locust Fork River website: flfr.org