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.
Buckskin Gulch
The Buckskin Gulch, a canyon in southern Utah, is one of the main tributaries of the Paria River, which is itself a minor tributary of the Colorado River. It is the longest and deepest slot canyon in the southwest United States and may be the longest in the world. As such it is one of the premier destinations for slot canyon hikers, and receives a high amount of foot traffic.