The McCloud River watershed drains . It rises from several spring-fed streams in Colby Meadows in the Cascades approximately southeast of Mount Shasta in Siskiyou County. It flows initially west, passing south of Mount Shasta and receiving streams that drain the southern slope of the peak. East of McCloud it forms a series of waterfalls which tumble over basaltic lava flows, known collectively as the McCloud River Falls or Falls of the McCloud River.