East Fork Owyhee River, c.110 mi/177 km long, in Nev. and Idaho; rises in N part of Elko co., NE Nev.; flows NW, past Mountain City and Owyhee, into Owyhee co., SW Idaho, and joins South Fork Owyhee R. near Oregon state line. Artificial reservoir in upper course, 12 mi/19 km SE of Mountain City.