The Stanislaus River headwaters consist of three forks in the high Sierra Nevada, in parts of Alpine County, Calaveras County and Tuolumne County. The Middle Fork, long, is the largest tributary and is sometimes considered part of the main stem. It begins in the Emigrant Wilderness of the Stanislaus National Forest about west of Sonora Pass. It flows northwest then west, receiving the Clark Fork below Dardanelle, before feeding Donnell Lake and Beardsley Lake, both formed by hydroelectric power dams. Below the Beardsley dam, it continues west to its confluence with the North Fork at Camp Nine, a popular swimming and fishing area near Hathaway Pines. The -long North Fork rises in the Carson-Iceberg Wilderness and flows in a generally southwest direction to its confluence with the Middle Fork, passing through several small hydropower dams. For most of their lengths, both forks flow in deep canyons through rugged, heavily forested terrain. The total length of the Stanislaus River, measured from its mouth to the head of Kennedy Creek in the Emigrant Wilderness, is about .