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.
Missouri River
The Missouri's headwaters above Three Forks extend much farther upstream than the main stem. Measured to the farthest source at Brower's Spring, the Jefferson River is long. Thus measured to its highest headwaters, the Missouri River stretches for . When combined with the lower Mississippi, the Missouri and its headwaters form part of the fourth-longest river system in the world, at .