It rises as two forks in the Six Rivers National Forest in Trinity County; the West Fork is the larger of the two branches. The West Fork begins at Johnson Spring on the northeastern flank of an unnamed ridge at an elevation of 5,992 feet (1,826 m).^[1] From there, it flows north about 16.5 miles (26.6 km) to its confluence with the East Fork at 40°37′49″N 123°20′48″W / 40.6304°N 123.3466°W / 40.6304; -123.3466.^[2] The East Fork rises on the south flank of West Redina Peak at 5,416 feet (1,651 m)^[3] and flows northwest for 14.2 miles (22.9 km) to the confluence.

From the confluence, Copper Creek proceeds to flow north-northwest, looping to the southeast at the confluence with Basin Creek. It then turns north again, meandering through a relatively straight valley, and receives in quick succession Graham Creek and Lost Cow Creek from the right. At the confluence with Indian Creek, the creek swings northwest, crossing the Humboldt County line and looping along the east flank of Salmon Mountain. From there, the river proceeds north-northwest through a canyon flanked by the copper-colored cliffs that were responsible for the origin of its name—before receiving Little Copper Creek from the left and emptying into the Klamath River 3 miles (4.8 km) downstream of the city of Orleans. The Klamath flows a further 40 miles (64 km) to empty into the Pacific Ocean.^[4][5]

Historically, the Hupa tribe lived along Copper Creek and the Klamath River around the area of the Copper's mouth. The river was called Chwuloq'e, meaning chinook salmon. One Hupa village was located on the creek, within 5 miles (8.0 km) of the mouth. The river received its modern name in 1851 when miners attracted by the California Gold Rush found the river while traveling on the Klamath in search of gold. The copper-colored cliffs that line the last few miles of the creek's canyon inspired them to give the stream its present name.^[6] The miners eventually employed hydraulic mining in order to find deeper deposits of gold in the hillsides surrounding the river. This practice severely hurt the ecology of the creek and its salmon run.^[7]

• List of rivers of California

• Durham, David L. (1998). California's geographic names: a gazetteer of historic and modern names of the state. Quill Driver Books. ISBN 1-884995-14-4.
• Gudde, Erwin G.; Bright, William (2004). California Place Names: The Origin and Etymology of Current Geographical Names. University of California Press. ISBN 0-520-24217-3.
• Palmer, Tim (1993). The wild and scenic rivers of America. Island Press. ISBN 1-55963-145-7.