Big Sioux River
| Big Sioux River | ||
 Big Sioux River catchment area |
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| Data | ||
| Water code | US : 1253923 | |
| location | South Dakota , Iowa (USA) | |
| River system | Mississippi River | |
| Drain over | Missouri → Mississippi → Gulf of Mexico | |
| source | in Roberts County , South Dakota, 45 ° 19 ′ 18 ″ N , 97 ° 2 ′ 33 ″ W |
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| muzzle | in the Missouri River near Sioux City Coordinates: 42 ° 29 '24 " N , 96 ° 27' 0" W 42 ° 29 '24 " N , 96 ° 27' 0" W
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| length | 470 km | |
| Medium-sized cities | Sioux Falls , Sioux City | |
 Waterfalls in Sioux Falls |
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The Big Sioux River is a 250-mile left tributary of the Missouri River in eastern South Dakota and northwestern Iowa .
The Big Sioux River has its source in Roberts County , South Dakota. It then flows through Grant , Codington , Hamlin , Brookings , Moody and Minnehaha Counties . At Sioux Falls , the river forms a waterfall that gave the city its name. According to Brandon , the river flows along the border of the two states of South Dakota and Iowa .