Mississippi became a Territory in 1798
Mississippi became a State on December 10, 1817

Alabama became a Territory in 1817
Alabama became a State on December 14, 1819

Arkansas bought in 1803 and became a subdivision of Louisiana
Arkansas became a county in Missouri Territory in 1812
Arkansas became a Territory in 1819
Arkansas became a State on June 6, 1836

Louisiana Purchase south of 33 degrees (including West Florida) became Territory of  Orleans in 1804
Louisiana Purchase north of 33 degrees became Louisiana Territory in 1805 and Missouri Territory in 1812
Louisiana became a State on April 30, 1812

Tennessee annexed to North Carolina and became Washington Co. in 1776
Washington Co. ceded to U.S. government in 1784,  but NC revoked cession, but not before the eastern section had formed the short lived State of Franklin.
Second cession by NC accepted in 1790 and was organized as the Terrirory of the United States South of the River Ohio
Tennessee became a State on June 1, 1796
Cherokee treaties between 1798 and 1819 ended their claims, except in the southeastern corner of Tennesse
Chickasaw lands in the west Tennessee were bought in 1818.
Cherokee were forced out of Tennessee in 1838 and the area was opened to settlement

   A
Adams County
    1799, formed as one of two counties in MS Territory, above Florida
    1800, lost central and eastern part to form Washington Co., AL
    1802, lost south part to form Wilkinson Co., gained some from Jefferson Co.
    1809, lost central and east to Franklin Co., and some to Jefferson Co.
    1810, gained some from Wilkinson Co.
    1846, lost land to Wilkinson Co.
    1882, gained land from Wilkinson Co.
    1884, lost land to Wilkinson Co.
    1914, exchanged land with Wilkinson Co.
Alcorn County
    1870, formed from northwest half of Tishomingo Co. and Tippah Co.
Amite County
    1809, formed from central and eastern Wilkinson Co., and lost some to Franklin Co.
    1810, lost some land to Franklin Co.
    1819, gained land from Franklin Co.
    1821, gained land from Wilkinson Co.
    1870, lost land to form Lincoln Co.
    1871, gained land from Franklin Co. and Lincoln Co.
    1873, lost land to Franklin Co.  Lost land to Lincoln Co.
Attala County
    1833, formed from north half of Madison Co
   B
Bainbridge County
    1823, formed from west two thirds of Covington Co.
    1824, merged into Covington Co.
Benton County
    1870, formed from Marshall Co. and Tippah Co.
    1871, exchanged land with Marshall Co.
    1876, exchanged land with Marshall Co.
Biloxi Parish, Feliciana Co., Orleans Territory
    1811, formed by Orleans Territory around Biloxi area, west of Pascagoula Parish
Bolivar County
    1836, formed from Tallahatchie Co., Washington, and non-county area
    1842, gained land from Coahoma Co.
    1844, lost east half to form Sunflower Co.
    1871, lost land to Sunflower Co.  Lost land to Washington Co.
Bourbon County
    1785, formed in SW corner of MS, in Natchez District area, formed by Georgia
    1789, disolved
   C
Calhoun County
    1852, formed from Chickasaw Co., Lafayette Co., and Yalobusha Co.
Carroll County
    1833, formed from Lowndes Co., Monroe Co., Washington Co., and Yazoo Co.
    1871, lost land to form Leflore Co.  Lost land to form Montgomery Co.
    1877, gained land from Leflore Co.
    1880, lost land to Leflore Co.
    1882, exchanged land with Montgomery Co.
    1896, gained land from Leflore Co.
Cherokee Lands
    1804, all land in MS north of Choctaw Lands, except a small section in NE corner of MS
    1816, ceded some eastern lands in AL and MS
    1870, lost land to form Grenada Co.
Chickasaw County
    1836, formed from Monroe Co. and non-county lands
    1852, lost land to form Calhoun Co.
    1854, gained land from Choctaw Co.
    1871, lost land to form Colfax Co.
    1874, lost land to form Sumner Co.
    1875, gained land from Montgomery Co.  Lost land to Sumner Co.
Chicot County, Arkansas
    1823, created from Arkansas Co.
Choctaw County
    1833, formed from Lowndes Co., Madison Co., Monroe Co., and Yazoo Co.  Non-county land to north attached to county.
    1854, lost land to Chickasaw Co.
    1870, lost land to form Grenada Co.
    1871, lost land to form Montgomery Co.
    1874, lost land to form Sumner Co.  Gained land from Winston Co.
    1875, exchanged land with Sumner Co.  Lost land to Winston Co.
Choctaw County, Alabama
    1847, created December 29, from Sumter and Washington Counties
Choctaw Lands
    1804, non-county area west of Washington Co., AL, all central MS, and some NW MS
    1816, ceded some eastern lands in AL and MS
    1820, Treaty of Doak's Stand, Choctaw Cession of about half their land on the east
Claiborne County
    1802, formed from NW Pickering Co.
    1809, lost north to form Warren Co.
    1811, gained from Jefferson Co.
    1820, lost land to Jefferson Co.
    1829, gained some land from Warren Co.
Clarke County
    1833, formed from Wayne Co.
    1871, lost land to Wayne Co.
Clay County
    1876, created by renaming Colfax Co.
Coahoma County
    1836, formed from non-county area
    1842, lost land to Bolivar Co.  Gained land from Tunica Co.
    1843, gained land from Tunica Co.
    1844, gained land from Tunica Co.
    1848, lost land to Tunica Co.
    1877, lost land to form Quitman Co.
Colbert County, Alabama
    1867, created February 6, from Franklin Co.  Abolished same year.
    1870, recreated from Franklin Co.
Colfax County
    1871, formed from Chickasaw Co., Lowndes Co., Monroe Co., and Oktibbeha Co.
    1876, renamed Clay County
Concordia Parish, Louisiana
    1805, created from Avoyelles Parish
Copiah County
    1823, formed from south quarter of Hinds Co., and part of Franklin Co.
    1824, lost east half to form Simpson Co.
    1870, lost land to form Lincoln Co.
Covington County
    1819, formed from west Wayne Co. and east Lawrence Co.
    1822, lost to Wayne Co.
    1823, lost west two thirds to form Bainbridge Co.
    1824, regained Bainbridge Co.
    1825, gained from Lawrence Co. and Wayne Co.
    1826, lost to form Jones Co.
    1830, gained attached non-county land to north
    1833, lost land to form Scott Co.  Lost land to form Smith Co.
    1880, lost land to Marion Co.
    1906, lost land to form Jefferson Davis Co.
Crittenden County, Arkansas
    1825, created from Phillips Co.
   D
Davis County
    1865, created by renaming Jones Co.
    1869, renamed Jones Co.
Desha County, Arkansas
    1838, created from Arkansas Co. and Union Co.
DeSoto County
    1836, formed from Monroe Co. and Washington Co.
    1873, lost south land to form Tate Co.  Lost land to Marshall Co.
    1876, gained land from Tate Co.
    1878, gained land from Marshall Co.
   E
East Carroll Parish, Louisiana
    1877, created from Carroll Parish
East Feliciana Parish, Louisiana
    1824, created from Feliciana Parish
   F
Fayette County, Tennessee
    1824, created September 29 from Shelby County and Hardeman County
Feliciana Co., Orleans Territory
    1810, formed by Orleans Territory from West Florida, US now controls all but Mobile area under Spanish control
Forrest County
    1906, formed from west half of Perry Co. but unorganized
    1908, organized
Franklin County
    1809, formed mainly from central and east Adams, with some from Amite Co., Wilkinson Co., and non-county territory.  Lost some to Jefferson Co.
    1810, gained some from Amite Co.
    1819, lost to Amite Co.
    1822, gained from Jefferson Co.
    1823, lost to form Copiah Co.  Lost to Jefferson Co.
    1870, lost land to form Lincoln Co.
    1871, lost land to Amite Co.
    1873, gained land from Amite Co.
    1875, gained land from Lincoln Co.
Franklin County, Alabama
    1818, created February 6 from Cherokee Cession of 1816
   G
George County
    1910, formed from Greene Co. and Jackson Co.
Greene County
    1811, formed from SE Wayne Co.
    1817, lost some land to AL
    1820, gained land from AL.  Lost west land to form Perry Co.
    1822, gained land from Jackson Co.
    1823, gained land from Jackson Co.
    1871, lost land to Perry Co.
    1910, lost land to form George Co.
Grenada County
    1870, formed from Carroll Co., Choctaw Co., Tallahatchie Co., and Yalobusha Co.
   H
Hamilton County, Tennessee   (Eastern TN, not adjacent to MS)
    1819, created October 25 from Rhea Co.
Hancock County
    1812, formed from west third of West Florida made part of Mississippi Territory
    1824, lost land to Jackson Co.
    1828, gained land from Jackson Co.
    1833, gained land from Jackson Co.
    1836, lost land to Jackson Co.
    1841, lost land to form Harrison Co.
    1843, gained land from Marion Co.
    1844, lost land to Marion Co.
    1872, lost north half of land to form Pearl Co.
    1878, merged with part of Pearl Co.
    1890, lost land to form Pearl River Co.
Hardeman County, Tennessee
    1823, created from Hardin Co. and Hardin Co.
Hardin County, Tennessee
    1819, created in November from Western District
Harrison County
    1841, formed from Hancock Co. and Jackson Co.
    1844, gained land from Jackson Co. and Perry Co.
    1846, lost land to Jackson Co.
    1875, gained land from Jackson Co.
    1916, lost north to form Stone Co.
Hinds County
    1821, formed from non-county area from Choctaw Cession of 1820
    1823, lost south quarter to form Copiah Co.  Lost north half to form Yazoo Co.  Lost some to Warren Co.
    1828, lost east half to form Rankin Co.
    1829, lost to Madison Co.
    1840, exchanged land with Madison Co.
Holmes County
    1833, formed from Yazoo Co.  Non-county land to northwest attached to county.
    1918, lost land to form Humphreys Co.
Humphreys County
    1918, formed from Holmes Co., Sunflower Co., Washington Co., and Yazoo Co.
   I
Issaquena County
    1844, formed from south half of Washington Co.
    1850, lost land to Yazoo Co.
    1876, lost land to form Sharkey Co.  Gained land from Warren Co.  Lost land to non-county area
    1890, gained land from non-county area
Itawamba County
    1836, formed from Monroe Co.
    1866, lost west third of land to form Lee Co.
    1870, lost land to form Prentiss Co.  Lost land to Tishomingo Co.
   J
Jackson County
    1812, formed from middle third of West Florida made part of Mississippi Territory
    1817, lost east to AL
    1820, gained from AL
    1822, lost to Greene Co.
    1823, lost to Greene Co.
    1824, gained from Hancock Co.
    1828, lost to Hancock Co. and Perry Co.
    1833, lost to Hancock Co.
    1836, gained land from Hancock Co.
    1841, lost land to form Harrison Co.
    1844, lost land to Harrison Co.
    1846, gained land from Harrison Co.
    1875, lost land to Harrison Co.
    1910, lost land to form George Co.
Jasper County
    1833, formed from south central Jones Co. and from some of Wayne Co.
Jefferson County
    1802, formed from SW Pickering County
    1809, gained some from Adams Co. and Franklin Co.
    1811, lost some to Claiborne Co.
    1820, gained land from Claiborne Co.
    1822, lost to Franklin Co.
    1823, gained from Franklin Co.
Jefferson Davis County
    1906, formed from Covington Co. and Lawrence Co.
Jones County
    1826, formed from parts of Covington Co. and Wayne Co.
    1830, gained attached non-county land to north
    1833, lost south central part to form Jasper Co.  Lost land to form Neshoba Co.  Lost land to form Scott Co.  Lost land to form Smith Co.
    1865, renamed Davis Co.
    1869, renamed Jones Co.
   K
Kemper County
    1833, formed from Lowndes Co., Rankin Co., and Wayne Co.
   L
Lafayette County
    1836, formed from Monroe Co.
    1846, lost land to Marshall Co.
    1850, lost land to Marshall Co.
    1852, lost land to form Calhoun Co.
    1854, lost land to Marshall Co.
    1871, gained land from Marshall Co.
    1873, lost land to Yalobusha Co.
Lamar County
    1904, formed from Marion Co. and Pearl River Co.
Lamar County, Alabama
    1868, created February 4 from Marion and Fayette Counties with name Sanford Co.
    1877, Sanford Co. renamed
Lauderdale County
    1833, formed from Rankin Co. and Wayne Co.
Lauderdale County, Alabama
    1818, created February 6 from Cherokee and Chickasaw Cession of 1816
Lawrence County
    1814, formed from north Marion Co.
    1819, lost east land to form Covington Co.  Lost land to Marion Co.
    1825, lost land to Pike Co.  Lost land to Covington Co.
    1827, lost land to Pike Co.
    1870, lost land to form Lincoln Co.
    1878, lost land to Lincoln Co.
    1880, gained land from Pike Co.
    1884, gained land from Marion Co.  Gained land from Pike Co.
    1906, lost land to form Jefferson Davis Co.
    1908, exchanged land with Pike
Leake County
    1833, formed from central part of Madison Co., and from some of Rankin Co.
Lee County
    1866, formed from west third of Itawamba Co. and from Pontotoc Co.
    1870, lost land to form Union Co.  Lost land to Pontotoc Co.
    1873, gained land from Union Co.
    1874, lost land to Union Co.
Lee County, Arkansas
    1873, created from Crittenden Co., Monroe Co., Phillips Co., and St. Francis Co.
Leflore County
    1871, formed from Carroll Co. and Sunflower Co.
    1877, lost land to Carroll Co.
    1880, gained land from Carroll Co.
    1896, lost land to Carroll Co.
Lincoln County
    1870, formed from Amite Co., Copiah Co., Franklin Co., Lawrence Co., and Pike Co.
    1871, lost land to Amite Co.
    1873, gained land from Amite Co.
    1875, lost land to Franklin Co.
    1878, gained land from Lawrence Co.
Lowndes County
    1830, formed from most of Monroe Co. (the 1816 Chickasaw Cession) and southern attached non-county lands
    1831, gained land from Madison Co., Rankin Co., and Wayne Co.
    1833, lost land to form Carroll Co.  Lost land to form Choctaw Co.  Lost land to form Kemper Co.  Lost land to form Noxubee Co.  Lost land to form Oktibbeha Co.  Lost land to form Winston Co.
    1871, lost land to form Colfax Co.
   M
Madison County
    1828, formed from east half of Yazoo Co.
    1829, gained from Hinds Co.  Some non-county areas of unceded Indian lands (mostly Choctaw) are attached to county.
    1830, gained attached non-county land to northeast
    1831, lost land to Lowndes Co.
    1833, lost north half to form Attala Co.  Lost land to form Choctaw Co.  Lost some central part to form Leake Co.  Lost land to form Neshoba Co.  Lost land to form Winston Co.  Gained from Rankin Co.
    1838, lost land to Scott Co.
    1840, exchanged land with Hinds Co.
    1859, lost land to Scott Co.
Madison Parish, Louisiana
    1838, created from Concordia Parish
Marion County
    1811, formed from west Wayne Co., east Amite, east Franklin, and non-county territory
    1814, lost north to form Lawrence Co.
    1815, lost west to form Pike Co.
    1819, gained from Lawrence Co.
    1843, lost land to Hancock Co.
    1844, gained land from Hancock Co.
    1876, lost land to Pearl Co.
    1878, merged with part of Pearl Co.
    1880, gained land from Covington Co.
    1884, lost land to Lawrence Co.
    1890, lost land to form Pearl River Co.
    1904, lost land to form Lamar Co.
    1912, lost land to form Walthall Co.
Marion County, Alabama
    1818, created February 13
Marshall County
    1836, formed from Monroe Co.
    1846, gained land from Lafayette Co.
    1850, gained land from Lafayette Co.
    1854, gained land from Lafayette Co.
    1870, lost land to form Benton Co.
    1871, exchanged land with Benton Co.  Lost land to Lafayette Co.
    1873, lost land to form Tate Co.  Gained land from DeSoto Co.
    1876, exchanged land with Benton Co.
    1878, lost land to DeSoto Co.
McNairy County, Tennessee
    1823, created October 8 from Hardin Co.
Mobile County, Alabama
    1812, created December 18 from Baldwin Co. and east third of West Florida made part of Mississippi Territory, from Mobile east still under Spanish control
    1913, US captured Mobile extending full control over West Florida
    1817, became county in Alabama Territory
Monroe County
    1821, formed from non-county area from Chickasaw Cession of 1816
    1829, some non-county areas of unceded Indian lands (almost all Chickasaw) are attached to county.
    1830, lost most of Chickasaw Cession of 1816, and southern part of attached lands to form Lowndes Co.
    1830, gained attached non-county land to north and west
    1833, lost land to form Carroll Co.  Lost land to form Choctaw Co.  Lost land to form Yalobusha Co.
    1836, lost land to form Chickasaw Co.
    1836, lost land to form Itawamba Co.  Lost land to form Lafayette Co.  Lost land to form Marshall Co.   Lost land to form Pontotoc Co.  Lost land to form Tippah Co.  Lost land to form Tishomingo Co.  Lost land to form Panola Co.
    1871, lost land to form Colfax Co.
Montgomery County
    1871, formed form Carroll Co. and Choctaw Co.
    1874, lost land to form Sumner Co.
    1875, lost land to Choctaw Co.  Gained land from Sumner Co.
    1882, exchanged land with Carroll Co.
   N
Neshoba County
    1833, formed from Jones Co., Madison Co., Rankin Co., and Wayne Co.
    1836, lost south half to form Newton Co.
    1873, lost land to Winston Co.
Newton County
    1836, formed from south half of Neshoba Co.
Noxubee County
    1833, formed from Lowndes Co. and Rankin Co.
   O
Oktibbeha County
    1833, formed from Lowndes Co.
    1871, lost land to form Colfax Co.
    1875, lost land to Sumner Co.
Orleans Territory
    1804, formed from territory claimed by US and Spain including West Florida
    1811, all but Mobile area brought under US control
    1812, West Florida from the Pearl River to the Perdido River is made part of Mississippi Territory, from Mobile east still under Spanish control
   P
Panola County
    1836, formed from Monroe Co. Washington Co., and non-county area
    1841, gained land from Tunica Co.
    1871, lost land to Tunica Co.
    1877, lost land to form Quitman Co.
Pascagoula Parish, Feliciana Co., Orleans Territory
    1811, formed by Orleans Territory in far east part of Feliciana Co.
Pearl County
    1872, formed from north half of Hancock Co.
    1876, gained land from Marion Co.
    1878, merged into Hancock Co. and Marion Co.
Pearl River County
    1890, formed from Hancock Co. and Marion Co.
    1904, lost land to form Lamar Co.
Perry County
    1820, formed from west Greene Co.
    1825, gained from Hancock Co.
    1828, gained from Jackson Co.
    1844, lost land to Harrison Co.
    1871, gained land from Greene Co.
    1906, lost west half of land to form Forrest Co.
Phillips County, Arkansas
    1820, created from Arkansas Co. and Lawrence Co.
Pickens County, Alabama
    1820, created December 20 from Marion Co. and Tuscaloosa Co.
Pickering County
    1799, formed as one of two original counties in MS Territory, above Adams Co.
    1802, lost north to form Claiborne Co., lost east to non-county area, and name changed to Jefferson Co.
Pike County
    1815, formed from west Marion Co.
    1825, gained land from Lawrence Co.
    1827, gained land from Lawrence Co.
    1870, lost land to form Lincoln Co.
    1880, lost land to Lawrence Co.
    1884, lost land to Lawrence Co.
    1908, exchanged land with Lawrence
    1912, lost land to form Walthall Co.
Pontotoc County
    1836, formed from Monroe Co.
    1866, lost land to form Lee Co.
    1870, lost land to form Union Co.  Gained land from Lee Co.
    1873, lost land to Union Co.
Prentiss County
    1870, formed from southwest  two thirds of Tishomingo Co. and Itawamba Co.
    1874, gained land from Union Co.
    1876, lost land to Tishomingo Co.
   Q
Quitman County
    1877, formed from Coahoma Co., Panola Co., Tallahatchie Co., and Tunica Co.
   R
Rankin County
    1828, formed from east half of Hinds Co.
    1829, jointly with Simpson Co.,  some non-county areas of unceded Indian lands (mostly Choctaw) are attached to counties.
    1830, gained attached non-county land to northeast
    1831, lost land to Lowndes Co.
    1833, lost land to form Kemper Co.  Lost land to form Lauderdale Co.  Lost land to form Leake Co.  Lost land to form Neshoba Co.  Lost land to form Noxubee Co.  Lost land to form Scott Co.  Lost land to form Smith Co.  Lost land to form Winston Co.  Lost land to Madison Co.
    1838, lost land to Scott Co.
   S
Saint Helena Parish, Louisiana
    1810, created from West Florida
Saint Tammany Parish, Louisiana
    1810, created from West Florida
Scott County
    1833, formed from Covington Co., Jones Co., and Rankin Co.
    1838, gained land from Madison Co. and Rankin Co.
    1859, gained land from Madison Co.
Sharkey County
    1876, formed from Issaquena Co., Warren Co., and Washington Co.
Shelby County, Tennessee
    1819, created November 24 from Western District
Simpson County
    1824, formed from east half of Copiah Co.
    1829, jointly with Rankin Co., some non-county areas of unceded Indian lands (mostly Choctaw) are attached to counties.
Smith County
    1833, formed from Covington Co., Jones Co., and Rankin Co.
Stone County
    1916, formed from north Harrison Co.
Sumner County
    1874, formed from Montgomery Co., Chickasaw Co., and Choctaw Co.
    1875, lost land to Montgomery Co.  Gained land from Chickasaw Co.  Gained land from Oktibbeha Co.  Exchanged land with Choctaw Co.
    1882, renamed Webster Co.
Sumter County, Alabama
    1832, created December 18 from Choctaw Cession of 1832
Sunflower County
    1844, formed from east half of Bolivar Co.
    1860, gained land from Tallahatchie Co.
    1871, lost land to form Leflore Co.  Gained from Bolivar Co. and Washington Co.
    1918, lost land to form Humphreys Co.
   T
Tallahatchie County
    1833, formed from Washington Co. and Yazoo Co.  Non-county land to north attached to county.
    1836, lost land to form Bolivar Co.  Gained land from non-county area
    1860, lost land to Sunflower Co.
    1870, lost land to form Grenada Co.
    1877, lost land to form Quitman Co.
Tangipahoa Parish, Louisiana
    1869, created from Livingston Parish, St. Tammany Parish, St. Helena Parish, and Washington Parish
Tate County
    1873, formed from south DeSoto Co. and Marshall Co.
    1876, lost land to DeSoto Co.  Gained land from Tunica Co.
Tensas Parish, Louisiana
    1843, created from Concordia Parish
Tippah County
    1836, formed from Monroe Co.
    1870, lost land to form Alcorn Co.  Lost land to form Benton Co.  Lost land to form Union Co.
Tishomingo County
    1836, formed from Monroe Co.
    1870, lost northwest half of land to form Alcorn Co.  Lost southwest two thirds of land to form Prentiss Co.  Gained land from Itawamba Co.
    1876, gained land from Prentiss Co.
Tunica County
    1836, formed from Washington Co. and non-county area
    1841, lost land to Panola Co.
    1842, lost land to Coahoma Co.
    1843, lost land to Coahoma Co.
    1844, lost land to Coahoma Co.
    1848, gained land from Coahoma Co. and non-county area
    1871, gained land from Panola Co.
    1876, lost land to Tate Co.
    1877, lost land to form Quitman Co.
   U
Union County
    1870, formed form Lee Co., Pontotoc Co., and Tippah Co.
    1873, lost land to Lee Co.  Gained land from Pontotoc Co.
    1874, lost land to Prentiss Co.  Gained land from Lee Co.
   V
   W
Walthall County
    1912, formed from Marion Co. and Pike Co., unorganized
    1914, organized
Warren County
    1809, formed from north Claiborne Co. and non-county area
    1821, gained land from non-county area, from Choctaw Cession of 1820
    1823, gained land from Hinds Co.
    1827, lost land to form Washington Co.
    1828, gained land from Washington Co.
    1829, lost to Claiborne Co.  Exchanged some land with Yazoo Co.
    1833, gained land from Yazoo Co.
    1839, gained land from Washington Co.
    1846, gained land from Yazoo Co.
    1852, gained land from Yazoo Co.
    1854, gained land from Yazoo Co.
    1873, gained land from Yazoo Co.
    1876, lost land to form Sharkey Co.  Lost land to Issaquena Co.
Washington County
    1827, formed from Warren and west half of Yazoo Co.
    1828, lost to Warren Co. and Yazoo Co.
    1829, some non-county areas of unceded Indian lands (mostly Choctaw) in northwest corner of state are attached to county.
    1830, gained attached but not contiguous non-county land north of Yazoo Co.
    1833, lost land to form Carroll Co.  Lost land to form Tallahatchie Co.  Lost land to form Yalobusha Co.  Lost land to Yazoo Co.
    1836, lost land to form Bolivar Co.  Lost land to form DeSoto Co.  Lost land to form Panola Co.  Lost land to form Tunica Co.
    1838, lost land to Warren Co.
    1844, lost south half to form Issaquena Co.
    1850, lost land to Yazoo Co.
    1871, lost land to Sunflower Co.  Gained land from Bolivar Co.
    1876, lost land to form Sharkey Co.
    1918, lost land to form Humphreys Co.
Washington County, Alabama
    1800, created June 4 from central and eastern Adams and Pickering Counties, Mississippi Territory
    1809, lost central and west to form Wayne Co., lost south to form Baldwin Co., AL, lost some to non-county area
    1812, lost east part to form Clarke Co., AL
    1817, became county in Alabama Territory
Washinton Parish, Louisiana
    1819, created from St. Tammany Parish
Wayne County
    1809, formed from central and west Washington Co., AL
    1811, lost SE to form Greene Co.  Lost west to form Marion Co.
    1817, lost some land to AL
    1819, lost west to form Covington Co.
    1820, gained from AL
    1822, gained from Covington Co.
    1825, lost to Covington Co.
    1826, lost to form Jones Co.
    1829, some non-county areas of unceded Indian lands (mostly Choctaw) are attached to county.
    1830, gained attached non-county land to north
    1831, lost land to Lowndes Co.
    1833, lost land to form Jasper Co.  Lost land to form Clarke Co.  Lost land to form Kemper Co.  Lost land to form Lauderdale Co.  Lost land to form Neshoba Co.  Lost land to form Tallahatchie Co.
    1871, gained land from Clarke Co.
Webster County
    1882, created by renaming Sumner Co.
West Feliciana Parish, Louisiana
    1824, created from Feliciana Parish
Wilkinson County
    1802, formed from south Adams Co.
    1809, lost central and east to form Amite Co. and some to Franklin Co.
    1810, lost some to Adams Co.
    1821, lost to Amite Co.
    1846, gained land from Adams Co.
    1882, lost land to Adams Co.
    1884, gained land from Adams Co.
    1914, exchanged land with Adams Co.
Winston County
    1833, formed from Lowndes Co., Madison Co., and Rankin Co.
    1873, gained land from Neshoba Co.
    1874, lost land to Choctaw Co.
    1875, gained land from Choctaw Co.
   X
   Y
Yalobusha County
    1833, formed from Monroe Co., Washington Co., and Yazoo Co.
    1852, lost land to form Calhoun Co.
    1870, lost land to form Grenada Co.
    1873, gained land from Lafayette Co.
Yazoo County
    1823, formed from north half of Hinds Co.
    1827, lost west half to form Washington Co.
    1828, lost east half to form Madison Co.  Gained from Washington Co.
    1829, exchanged some land with Warren Co.  Some non-county areas of unceded Indian lands (mostly Choctaw) are attached to county.
    1830, gained attached non-county land to north
    1833, lost land to form Carroll Co.  Lost land to form Holmes Co.  Lost land to form Choctaw Co.  Lost land to form Yalobusha Co.  Lost land to Warren Co.  Gained land from Washington Co.
    1846, lost land to Warren Co.
    1850, gained land from Issaquena Co. and Washington Co.
    1852, lost land to Warren Co.
    1854, lost land to Warren Co.
    1873, lost land to Warren Co.
    1918, lost land to form Humphreys Co.
   Z