Illinois River (Oregon)

Illinois River
Rafting the Green Wall Rapids on the Illinois River
Location of the mouth of the Illinois River in Oregon
EtymologyThe U.S. state of Illinois, the birthplace of three brothers named Althouse who emigrated to Oregon and mined for gold along Althouse Creek and the Illinois River
Location
CountryUnited States
StateOregon
CountyJosephine and Curry
Physical characteristics
SourceConfluence of East Fork Illinois River and West Fork Illinois River
 • locationnear Cave Junction, Josephine County, Oregon
 • coordinates42°09′35″N 123°39′33″W / 42.15972°N 123.65917°W / 42.15972; -123.65917
 • elevation1,271 ft (387 m)
MouthRogue River
 • location
Agness, Curry County, Oregon
 • coordinates
42°33′00″N 124°03′58″W / 42.55000°N 124.06611°W / 42.55000; -124.06611
 • elevation
102 ft (31 m)
Length56 mi (90 km)
Basin size983 sq mi (2,550 km2)
Discharge 
 • locationnear Kerby, 50.3 miles (81.0 km) from the mouth
 • average1,262 cu ft/s (35.7 m3/s)
 • minimum121 cu ft/s (3.4 m3/s)
 • maximum92,200 cu ft/s (2,610 m3/s)
TypeWild, Scenic, Recreational
Designated19 October 1984

The Illinois River is a tributary, about 56 miles (90 km) long, of the Rogue River in the U.S. state of Oregon. It drains part of the Klamath Mountains in northern California and southwestern Oregon. The river's main stem begins at the confluence of its east and west forks near Cave Junction in southern Josephine County. Its drainage basin includes Sucker Creek, which rises in the Red Buttes Wilderness, near Whiskey Peak on the California state line. The main stem flows generally northwest in a winding course past Kerby and through the Siskiyou National Forest and Kalmiopsis Wilderness. It joins the Rogue River from the south at Agness 4.75 miles NW of the Curry–Josephine county line, (US Geological Survey National Map measure tool) and 27 miles (43 km) from the Pacific Ocean, 16.8 miles as the crow flies.

The river's lower 50.4 miles (81.1 km), from where it enters the Rogue River–Siskiyou National Forest downstream from Kerby to its confluence with the Rogue River, were designated Wild and Scenic in 1984. Of this, 28.7 miles (46.2 km) is protected as wild, 17.9 miles (28.8 km) as scenic, and 3.8 miles (6.1 km) as recreational.