| COUNTY | YEAR FORMED | FROM | COUNTY SEAT |
|---|
| Adams | 1799 | Natchez District | Natchez |
| Alcorn | 1870 | Tippah / Tishomingo | Corinth |
| Amite | 1809 | Wilkinson | Liberty |
| Attala | 1833 | Choctaw Cession of 1830 | Kosciusko |
| Bainbridge | 1823 - | Historic - Created from Covington Co. Merged back into Covington Co in 1824 | |
| 1824 | | |
| Benton | 1870 | Marshall / Tippah | Ashland |
| Bolivar | 1836 | Choctaw Cession Of 1830 | Cleveland & Rosedale |
| Bourbon | 1785 - | Historic - Area of current Adams and Wilkinson county1. Formed | |
| 1788 | as early part of the Yazoo Land Faud. | |
| Calhoun | 1852 | Chickasaw / Lafayette / | Pittsboro |
| | Yalobusha | |
| Carroll | 1833 | Choctaw Cession | Carrollton & Vaiden |
| Chickasaw | 1836 | Chickasaw Cession of 1830 | Houston & Okolona |
| Choctaw | 1833 | Choctaw Cession | Ackerman |
| Claiborne | 1802 | Jefferson | Port Gibson |
| Clarke | 1833 | Choctaw Cession of 1830 | Quitman |
| Clay | 1871 | Chickasaw / Lowndes /Monroe / Oktibbeha | West Point |
| Coahoma | 1836 | Chickasaw Cession of 1836 | Clarksdale |
| Colfax | 1871 - 1876 | Historic - Created from | |
| | Chickasaw, Lowndes, Monroe, & Oktibbeha in 1871. Named changed to Clay in 1876. | |
| Copiah | 1823 | Hinds | Hazlehurst |
| | | |
| Covington | 1819 | Lawrence / Wayne | Collins |
| Davis | 1865 - 1869 | Historic - Jones Co changed | |
| | name to Davis in 1865, back | |
| | to Jones in 1869 | |
| DeSoto | 1836 | Indian Lands | Hernando |
| Forrest | 1906 | Perry | Hattiesburg |
| Franklin | 1809 | Adams | Meadville |
| George | 1910 | Greene / Jackson | Lucedale |
| Greene | 1811 | Amite / Franklin / Wayne | Leakesville |
| Grenada | 1870 | Carroll / Yalobusha / | Grenada |
| | Montgomery /Tallahatchie / | |
| | Webster / Choctaw | |
| Hancock | 1812 | Mobile District | Bay Saint Louis |
| Harrison | 1841 | Hancock / Jackson | Gulfport & Biloxi |
| Hinds | 1821 | Choctaw Cession of 1820 | Jackson & Raymond |
| Holmes | 1833 | Yazoo | Lexington |
| | | |
| Humphreys | 1918 | Holmes / Washington /Yazoo / Sunflower | Belzoni |
| | | |
| Issaquena | 1844 | Washington | Mayersville |
| Itawamba | 1836 | Chickasaw Cession of 1832 | Fulton |
| Jackson | 1812 | Mobile District | Pascagoula |
| | | |
| | | |
| Jasper | 1833 | Indian Lands | Bay Springs & Paulding |
| Jefferson | 1799 | Natchez | Fayette |
| | | |
| Jefferson | 1906 | Covington / Lawrence | Prentiss |
| Davis | | | |
| Jones | 1826 | Covington / Wayne | Laurel & Ellisville |
| Kemper | Choctaw Cession of 1830 | De Kalb | |
| Lafayette | 1836 | Chickasaw Cession | Oxford |
| Lamar | 1904 | Marion / Pearl River | Purvis |
| Lauderdale | 1833 | Choctaw Cession of 1833 | Meridian |
| Lawrence | 1814 | Marion | Monticello |
| Leake | 1833 | Choctaw Cession | Carthage |
| Lee | 1866 | Itawamba / Pontotoc | Tupelo |
| Leflore | 1871 | Carroll / Sunflower / | Greenwood |
| | Tallahatchie | |
| Lincoln | 1870 | Franklin / Lawrence /Copiah / | Brookhaven |
| | Pike / Amite | |
| Lowndes | 1830 | Monroe | Columbus |
| Madison | 1828 | Yazoo | Canton |
| Marion | 1811 | Amite / Wayne / Franklin | Columbia |
| Marshall | 1836 | Chickasaw Cession of 1832 | Holly Springs |
| Monroe | 1821 | Chickasaw Cession of 1821 | Aberdeen |
| | (Additional Monroe Information) | |
| Montgomery | 1871 | Carroll / Choctaw | Winona |
| Neshoba | 1833 | Choctaw Cession of 1830 | Philadelphia |
| Newton | 1836 | Neshoba | Decatur |
| | | |
| Noxubee | 1833 | Choctaw Cession of 1830 | Macon |
| | | |
| Oktibbeha | 1833 | Choctaw Cession of 1830 | Starkville |
| | | |
| Panola | 1836 | Chickasaw Cession of 1830 | Batesville & Sardis |
| | | |
| Pearl River | 1890 | Hancock / Marion | Poplarville |
| Perry | 1820 | Greene | New Augusta |
| Pickering | 1799 - | Historic - Claiborne formed | |
| 1802 | from Pickering, and name | |
| | changed to Jefferson in 1802. | |
| Pike | 1815 | Marion | Magnolia |
| Pontotoc | 1836 | Chickasaw Cession of 1832 | Pontotoc |
| Prentiss | 1870 | Tishomingo | Booneville |
| Quitman | 1877 | Panola / Coahoma | Marks |
| Rankin | 1828 | Hinds | Brandon |
| Scott | 1833 | Choctaw Cession of 1832 | Forest |
| Sharkey | 1876 | Warren / Washington / | Rolling Fork |
| | Issaquena | |
| Simpson | 1824 | Choctaw Cession of 1820 | Mendenhall |
| Smith | 1833 | Choctaw Cession of 1830 | Raleigh |
| Stone | 1916 | Harrison | Wiggins |
| Sumner | 1874 - | Historic - Created from Montgomery, Chickasaw, Choctaw Counties in 1874, and part of Oktibbeha in 1875. | |
| 1882 | Name changed to Webster in 1882. | |
| Sunflower | 1844 | Bolivar | Indianola |
| | | |
| Tallahatchie | 1833 | Choctaw Cession of 1830 | Charleston & Sumner |
| Tate | 1873 | Marshall / Tunica / DeSoto | Senatobia |
| Tippah | 1836 | Chickasaw Cession of 1832 | Ripley |
| Tishomingo | 1836 | Chickasaw Cession of 1832 | Iuka |
| Tunica | 1836 | Chickasaw Cession of 1832 | Tunica |
| Union | 1870 | Pontotoc /Tippah | New Albany |
| Walthall | 1910 | Marion / Pike | Tylertown |
| Warren | 1809 | Natchez District | Vicksburg |
| Washington | 1827 | Warren / Yazoo | Greenville |
| Wayne | 1809 | Mississippi Territory's | Waynesboro |
| | "Old" Washington county1 | |
| Webster | 1874 | Montgomery / Chickasaw / | Walthall |
| | Choctaw / Oktibbeha | |
| Wilkinson | 1802 | Adams | Woodville |
| Winston | 1833 | Choctaw Cession of 1830 | Louisville |
| | | |
| Yalobusha | 1833 | Choctaw Cession of 1830 | Water Valley & Coffeeville |
| Yazoo | 1823 | Hinds | Yazoo City |