| County | 1910 | 1915 |
|---|---|---|
| Armstrong | 231 | |
| Aurora | 6,143 | 6,736 |
| Beadle | 15,766 | 16,061 |
| Bennett | 1,488 | |
| Bonhomme | 11,061 | 11,560 |
| Brookings | 14,178 | 15,544 |
| Brown | 25,867 | 25,969 |
| Brule | 6,451 | 6,376 |
| Buffalo | 1,589 | 1,485 |
| Butte | 4.993 | 5,894 |
| Campbell | 5,244 | 4,888 |
| Charles Mix | 14,899 | 14,790 |
| Cheyenne River Res | ||
| Clark | 10,901 | 10,670 |
| Clay | 8,711 | 9,214 |
| Codington | 14,092 | 15,192 |
| Corson | 2,929 | 3,272 |
| Crow Creek Res | ||
| Custer | 4,458 | 3,452 |
| Davison | 11,625 | 13,005 |
| Day | 14,372 | 14,235 |
| Deuel | 7,768 | 8,529 |
| Dewey | 1,145 | 1,933 |
| Douglas | 6,400 | 6,639 |
| Edmunds | 7,654 | 6,845 |
| Fall River | 7,763 | 6,027 |
| Faulk | 6,716 | 5,265 |
| Grant | 10,303 | 10,474 |
| Gregory | 13,061 | 11,919 |
| Haakon* | 3,553 | |
| Hamlin | 7,475 | 7,791 |
| Hand | 7,870 | 7,286 |
| Hanson | 6,237 | 6,316 |
| Harding | 4,228 | 4,821 |
| Hughes | 6,271 | 5,055 |
| Hutchinson | 12,319 | 13,095 |
| Hyde | 3,307 | 2,685 |
| Jackson | 2,077 | |
| Jerauld | 5,120 | 5,275 |
| Kingsbury | 12,560 | 11,947 |
| Lake | 10,711 | 11,865 |
| Lawrence | 19,694 | 17,710 |
| Lincoln | 12,712 | 13,564 |
| Lower Brule Res | ||
| Lyman | 10,848 | 7,412 |
| McCook | 9,589 | 10,013 |
| McPherson | 6,791 | 6,831 |
| Marshall | 8,021 | 8,391 |
| Meade | 12,640 | 8,724 |
| Mellette | 1,700 | 3,427 |
| Miner | 7,661 | 8,007 |
| Minnehaha | 29,631 | 37,613 |
| Moody | 8,695 | 9,686 |
| Pennington | 12,453 | 10,040 |
| Perkins | 11,348 | 7,641 |
| Pine Ridge | 6,630 | 6,315 |
| Potter | 4,466 | 3,648 |
| Roberts | 14,897 | 15,660 |
| Rosebud Res | ||
| Sanborn | 6,607 | 7,377 |
| Spink | 15,981 | 14,977 |
| Standing Rock Res | ||
| Stanley | 14,975 | 2,251 |
| Sully | 2,462 | 2,004 |
| Tripp | 8,323 | 10,262 |
| Turner | 13,840 | 14,636 |
| Union | 10,676 | 11,436 |
| Walworth | 6,488 | 5,919 |
| Yankton | 13,135 | 14,851 |
| Ziebach | 2,571 | |
| Unorganized | 2,403 | |
| Total | 583,888 | 582,765 |
| * Formed from part of Stanley, 1914. |