Keya Paha River
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The Keya Paha River is a tributary of the Niobrara River, approximately 101 mi (163 km) long, in the U.S. states of South Dakota and Nebraska.
It rises in the prairie country of southeastern South Dakota, on the Rosebud Indian Reservation in Todd County near Antelope. It flows ESE into northeastern Nebraska and joins the Niobrara 10 mi. (16 km) west of Butte.
Between 1861 and 1882, the stretch of the Keya Paha from 43° N to its confluence with the Niobrara marked the boundary between Nebraska and the Dakota Territory.