The Pit River is the longest tributary of the Sacramento River and largest river in northeast California. It connects to the Sacramento River at Shasta Lake and has headwaters at the confluence of its two tributaries – the North and South Forks. It passes through mountain valleys and basalt flows, creating uniquely formed canyons. The main stem (from Shasta to where its tributaries connect 40 miles south of the California/Oregon border) is about 315 miles long. Its name derives from the pits dug along the river by the Achomawi Indians to serve as hunting traps.

The South Fork originates from the Warner Mountains of the Great Basin Range a few miles from the California/Nevada border. It flows west then ultimately north where it joins the North Fork, starting near Goose Lake. Together these forks push the river southwest and through forests and valleys, creating geologically unique canyons until it connects with the Fall River to enter the Sacramento River. The Pit River Watershed is comprised of several subwatersheds, including the Upper and Lower Pit rivers, Fall River, Goose Lake, Hat Creek and Burney Creek. The area is known for its wild trout, but industrialization and recent algal blooms have threatened water quality and habitat viability.