Rock River (Big Sioux River)

The Rock River is a tributary of the Big Sioux River, about 144 miles (232 km) long, in southwestern Minnesota and northwestern Iowa in the United States. Via the Big Sioux and Missouri rivers, it is part of the watershed of the Mississippi River. The river's name comes from a prominent rocky outcrop about 175 feet high (designated "The Rock" on Joseph Nicollet's 1843 map of the area) of reddish-gray Sioux Quartzite, about 3 miles (5 km) north of Luverne. The name is a translation of an older Dakota name Íƞyaƞ Ḣeyaka Wakpa, which Nicollet translates as "River of the Rock" but which could also be translated as "Rocky Hills River". The outcrop of quartzite is contained in Minnesota's Blue Mounds State Park.

Source: Wikipedia https://en.wikipedia.org/wiki/Rock_River_(Big_Sioux_River_tributary)