County
| FIPS Code [1] | County seat [2] | Established [2] | Formed from
| Etymology
| Population [2] | Area [2] | Map
|
| Aurora County | 003 | Plankinton | 1881 | Cragin and Wetmore counties | Aurora, Roman goddess of dawn | &0000000000003058.0000003,058 | &0000000000000708.000000708 sq mi (&0000000000001834.0000001,834 km2) |  |
| Beadle County | 005 | Huron | 1879 | Buchard, Clark, Kingsbury, and Spink counties | William Henry Harrison Beadle | &0000000000017023.00000017,023 | &0000000000001259.0000001,259 sq mi (&0000000000003261.0000003,261 km2) |  |
| Bennett County | 007 | Martin | 1909 | Lugenbeel, Shannon, Washabaugh, and Washington counties | Granville G. Bennett, justice of the Supreme Court for the Dakota Territory | &0000000000003574.0000003,574 | &0000000000001185.0000001,185 sq mi (&0000000000003069.0000003,069 km2) |  |
| Bon Homme County | 009 | Tyndall | 1862 | Unorganized territory | French word meaning "good man" | &0000000000007260.0000007,260 | &0000000000000563.000000563 sq mi (&0000000000001458.0000001,458 km2) |  |
| Brookings County | 011 | Brookings | 1862 | Unorganized territory | Wilmot Brookings, pioneer judge | &0000000000028220.00000028,220 | &0000000000000794.000000794 sq mi (&0000000000002056.0000002,056 km2) |  |
| Brown County | 013 | Aberdeen | 1879 | Beadle County | Alfred Brown, territorial legislator | &0000000000035460.00000035,460 | &0000000000001713.0000001,713 sq mi (&0000000000004437.0000004,437 km2) |  |
| Brule County | 015 | Chamberlain | 1875 | Charles Mix County | Brulé Sioux Native Americans | &0000000000005364.0000005,364 | &0000000000000819.000000819 sq mi (&0000000000002121.0000002,121 km2) |  |
| Buffalo County | 017 | Gann Valley | 1873 | Unorganized territory | American Bison | &0000000000002032.0000002,032 | &0000000000000471.000000471 sq mi (&0000000000001220.0000001,220 km2) |  |
| Butte County | 019 | Belle Fourche | 1883 | Harding | Buttes in the region | &0000000000009094.0000009,094 | &0000000000002249.0000002,249 sq mi (&0000000000005825.0000005,825 km2) |  |
| Campbell County | 021 | Mound City | 1873 | Buffalo | Newton B. Campbell, territorial legislator | &0000000000001782.0000001,782 | &0000000000000736.000000736 sq mi (&0000000000001906.0000001,906 km2) |  |
| Charles Mix County | 023 | Lake Andes | 1862 | Unorganized territory | Charles E Mix, commisioner of Indian Affairs | &0000000000009350.0000009,350 | &0000000000001098.0000001,098 sq mi (&0000000000002844.0000002,844 km2) |  |
| Clark County | 025 | Clark | 1873 | Hanson | Newton Clark, territorial legislator | &0000000000004143.0000004,143 | &0000000000000958.000000958 sq mi (&0000000000002481.0000002,481 km2) |  |
| Clay County | 027 | Vermillion | 1862 | Unorganized territory | Henry Clay | &0000000000013537.00000013,537 | &0000000000000412.000000412 sq mi (&0000000000001067.0000001,067 km2) |  |
| Codington County | 029 | Watertown | 1877 | Indian lands | Reverend G.S. Codington | &0000000000025897.00000025,897 | &0000000000000688.000000688 sq mi (&0000000000001782.0000001,782 km2) |  |
| Corson County | 031 | McIntosh | 1909 | Indian lands | Dighton Corson, a Justice of the South Dakota Supreme Court | &0000000000004181.0000004,181 | &0000000000002473.0000002,473 sq mi (&0000000000006405.0000006,405 km2) |  |
| Custer County | 033 | Custer | 1875 | Indian lands | General George Armstrong Custer | &0000000000007275.0000007,275 | &0000000000001558.0000001,558 sq mi (&0000000000004035.0000004,035 km2) |  |
| Davison County | 035 | Mitchell | 1873 | Hanson | Henry C. Davison, early resident of county | &0000000000018741.00000018,741 | &0000000000000436.000000436 sq mi (&0000000000001129.0000001,129 km2) |  |
| Day County | 037 | Webster | 1879 | Clark | Merrit H. Day, territorial legislator | &0000000000006267.0000006,267 | &0000000000001029.0000001,029 sq mi (&0000000000002665.0000002,665 km2) |  |
| Deuel County | 039 | Clear Lake | 1862 | Brookings | Jacob S. Deuel, pioneer legislator | &0000000000004498.0000004,498 | &0000000000000624.000000624 sq mi (&0000000000001616.0000001,616 km2) |  |
| Dewey County | 041 | Timber Lake | 1873 | Armstrong County and Indian lands | William P. Dewey, territorial surveyor-general | &0000000000005972.0000005,972 | &0000000000002303.0000002,303 sq mi (&0000000000005965.0000005,965 km2) |  |
| Douglas County | 043 | Armour | 1873 | Charles Mix | Stephen A. Douglas | &0000000000003458.0000003,458 | &0000000000000434.000000434 sq mi (&0000000000001124.0000001,124 km2) |  |
| Edmunds County | 045 | Ipswich | 1873 | Buffalo | Newton Edmunds, Governor of Dakota Territory | &0000000000004367.0000004,367 | &0000000000001146.0000001,146 sq mi (&0000000000002968.0000002,968 km2) |  |
| Fall River County | 047 | Hot Springs | 1883 | Custer | Fall River | &0000000000007453.0000007,453 | &0000000000001740.0000001,740 sq mi (&0000000000004507.0000004,507 km2) |  |
| Faulk County | 049 | Faulkton | 1873 | Unorganized lands | Andrew Jackson Faulk, Governor of Dakota Territory | &0000000000002640.0000002,640 | &0000000000001000.0000001,000 sq mi (&0000000000002590.0000002,590 km2) |  |
| Grant County | 051 | Milbank | 1873 | Codington and Deuel counties | Ulysses S. Grant, U.S. President and American Civil War general | &0000000000007847.0000007,847 | &0000000000000682.000000682 sq mi (&0000000000001766.0000001,766 km2) |  |
| Gregory County | 053 | Burke | 1862 | Unorganized territory | John Shaw Gregory, territorial legislator | &0000000000004792.0000004,792 | &0000000000001016.0000001,016 sq mi (&0000000000002631.0000002,631 km2) |  |
| Haakon County | 055 | Philip | 1914 | Stanley County | King Haakon VII of Norway | &0000000000002196.0000002,196 | &0000000000001813.0000001,813 sq mi (&0000000000004696.0000004,696 km2) |  |
| Hamlin County | 057 | Hayti | 1873 | Deuel County | Hannibal Hamlin, Vice-President and United States Senator | &0000000000005540.0000005,540 | &0000000000000511.000000511 sq mi (&0000000000001323.0000001,323 km2) |  |
| Hand County | 059 | Miller | 1873 | Buffalo County | George H. Hand, territorial official | &0000000000003741.0000003,741 | &0000000000001437.0000001,437 sq mi (&0000000000003722.0000003,722 km2) |  |
| Hanson County | 061 | Alexandria | 1873 | Buffalo and Deuel counties | Joseph R. Hanson | &0000000000003139.0000003,139 | &0000000000000435.000000435 sq mi (&0000000000001127.0000001,127 km2) |  |
| Harding County | 063 | Buffalo | 1909 | Unorganized lands | J.A. Harding | &0000000000001353.0000001,353 | &0000000000002671.0000002,671 sq mi (&0000000000006918.0000006,918 km2) |  |
| Hughes County | 065 | Pierre | 1880 | Buffalo County | Alexander Hughes | &0000000000016481.00000016,481 | &0000000000000741.000000741 sq mi (&0000000000001919.0000001,919 km2) |  |
| Hutchinson County | 067 | Olivet | 1862 | Unorganized territory | John Hutchinson | &0000000000008075.0000008,075 | &0000000000000813.000000813 sq mi (&0000000000002106.0000002,106 km2) |  |
| Hyde County | 069 | Highmore | 1873 | Buffalo County | James Hyde | &0000000000001671.0000001,671 | &0000000000000861.000000861 sq mi (&0000000000002230.0000002,230 km2) |  |
| Jackson County | 071 | Kadoka | 1914 | Stanley County | J.R. Jackson | &0000000000002930.0000002,930 | &0000000000001869.0000001,869 sq mi (&0000000000004841.0000004,841 km2) |  |
| Jerauld County | 073 | Wessington Springs | 1883 | Aurora County | H.A. Jerauld | &0000000000002295.0000002,295 | &0000000000000530.000000530 sq mi (&0000000000001373.0000001,373 km2) |  |
| Jones County | 075 | Murdo | 1916 | Lyman County | Jones County Iowa | &0000000000001193.0000001,193 | &0000000000000971.000000971 sq mi (&0000000000002515.0000002,515 km2) |  |
| Kingsbury County | 077 | De Smet | 1873 | Hanson County | George W. Kingsbury and T.A. Kingsbury | &0000000000005815.0000005,815 | &0000000000000838.000000838 sq mi (&0000000000002170.0000002,170 km2) |  |
| Lake County | 079 | Madison | 1873 | Brookings and Hanson counties | lakes within the county | &0000000000011276.00000011,276 | &0000000000000563.000000563 sq mi (&0000000000001458.0000001,458 km2) |  |
| Lawrence County | 081 | Deadwood | 1875 | Unorganized territory | John Lawrence | &0000000000021802.00000021,802 | &0000000000000800.000000800 sq mi (&0000000000002072.0000002,072 km2) |  |
| Lincoln County | 083 | Canton | 1867 | Unorganized territory | Abraham Lincoln | &0000000000024131.00000024,131 | &0000000000000578.000000578 sq mi (&0000000000001497.0000001,497 km2) |  |
| Lyman County | 085 | Kennebec | 1873 | Unorganized territory | W.P. Lyman | &0000000000003895.0000003,895 | &0000000000001640.0000001,640 sq mi (&0000000000004248.0000004,248 km2) |  |
| Marshall County | 091 | Britton | 1885 | Day County | Marshall Vincent | &0000000000004576.0000004,576 | &0000000000000839.000000839 sq mi (&0000000000002173.0000002,173 km2) |  |
| McCook County | 087 | Salem | 1873 | Hanson County | Edwin McCook | &0000000000005832.0000005,832 | &0000000000000575.000000575 sq mi (&0000000000001489.0000001,489 km2) |  |
| McPherson County | 089 | Leola | 1873 | Buffalo County | James B. McPherson | &0000000000002904.0000002,904 | &0000000000001137.0000001,137 sq mi (&0000000000002945.0000002,945 km2) |  |
| Meade County | 093 | Sturgis | 1889 | Lawrence County | George Meade | &0000000000024253.00000024,253 | &0000000000003471.0000003,471 sq mi (&0000000000008990.0000008,990 km2) |  |
| Mellette County | 095 | White River | 1909 | Lyman County | Arthur C. Mellette | &0000000000002083.0000002,083 | &0000000000001307.0000001,307 sq mi (&0000000000003385.0000003,385 km2) |  |
| Miner County | 097 | Howard | 1873 | Hanson County | Nelson Miner and Ephriam Miner | &0000000000002884.0000002,884 | &0000000000000570.000000570 sq mi (&0000000000001476.0000001,476 km2) |  |
| Minnehaha County | 099 | Sioux Falls | 1862 | Unorganized territory | Native American for waterfall | &0000000000148281.000000148,281 | &0000000000000809.000000809 sq mi (&0000000000002095.0000002,095 km2) |  |
| Moody County | 101 | Flandreau | 1873 | Brookings and Minnehaha counties | Gideon C. Moody | &0000000000006595.0000006,595 | &0000000000000520.000000520 sq mi (&0000000000001347.0000001,347 km2) |  |
| Pennington County | 103 | Rapid City | 1875 | Unorganized territory | John L. Pennington | &0000000000088565.00000088,565 | &0000000000002776.0000002,776 sq mi (&0000000000007190.0000007,190 km2) |  |
| Perkins County | 105 | Bison | 1909 | Butte and Harding counties | Henry E. Perkins | &0000000000003363.0000003,363 | &0000000000002872.0000002,872 sq mi (&0000000000007438.0000007,438 km2) |  |
| Potter County | 107 | Gettysburg | 1875 | Buffalo County | Joel A. Potter | &0000000000002693.0000002,693 | &0000000000000866.000000866 sq mi (&0000000000002243.0000002,243 km2) |  |
| Roberts County | 109 | Sisseton | 1883 | Grant County | S.G. Roberts | &0000000000010016.00000010,016 | &0000000000001101.0000001,101 sq mi (&0000000000002852.0000002,852 km2) |  |
| Sanborn County | 111 | Woonsocket | 1883 | Miner County | George W. Sanborn | &0000000000002675.0000002,675 | &0000000000000569.000000569 sq mi (&0000000000001474.0000001,474 km2) |  |
| Shannon County | 113 | Hot Springs | 1875 | Fall River County | Peter Shannon | &0000000000012466.00000012,466 | &0000000000002094.0000002,094 sq mi (&0000000000005423.0000005,423 km2) |  |
| Spink County | 115 | Redfield | 1873 | Hanson County | S.L. Spink | &0000000000007454.0000007,454 | &0000000000001504.0000001,504 sq mi (&0000000000003895.0000003,895 km2) |  |
| Stanley County | 117 | Fort Pierre | 1873 | Unorganized territory | David S. Stanley | &0000000000002772.0000002,772 | &0000000000001443.0000001,443 sq mi (&0000000000003737.0000003,737 km2) |  |
| Sully County | 119 | Onida | 1873 | Potter County | Alfred Sully | &0000000000001556.0000001,556 | &0000000000001007.0000001,007 sq mi (&0000000000002608.0000002,608 km2) |  |
| Todd County | 121 | Winner | 1909 | Meyer and Tripp counties | John Blair Smith Todd | &0000000000009050.0000009,050 | &0000000000001388.0000001,388 sq mi (&0000000000003595.0000003,595 km2) |  |
| Tripp County | 123 | Winner | 1873 | Unorganized territory | Bartlett Tripp | &0000000000006430.0000006,430 | &0000000000001614.0000001,614 sq mi (&0000000000004180.0000004,180 km2) |  |
| Turner County | 125 | Parker | 1871 | Lincoln County | John W. Turner | &0000000000008849.0000008,849 | &0000000000000617.000000617 sq mi (&0000000000001598.0000001,598 km2) |  |
| Union County | 127 | Elk Point | 1862 | Unorganized territory | pro-Union people during the civil war | &0000000000012584.00000012,584 | &0000000000000460.000000460 sq mi (&0000000000001191.0000001,191 km2) |  |
| Walworth County | 129 | Selby | 1873 | Buffalo County | Walworth County Wisconsin | &0000000000005974.0000005,974 | &0000000000000708.000000708 sq mi (&0000000000001834.0000001,834 km2) |  |
| Yankton County | 135 | Yankton | 1862 | Unorganized territory | Yankton Sioux Native Americans | &0000000000021652.00000021,652 | &0000000000000522.000000522 sq mi (&0000000000001352.0000001,352 km2) |  |
| Ziebach County | 137 | Dupree | 1911 | Armstrong, Schnasse, and Sterling counties | Frank M. Ziebach | &0000000000002519.0000002,519 | &0000000000001962.0000001,962 sq mi (&0000000000005082.0000005,082 km2) |  |
Darker colors indicate heavier density.