| S.N. | County | FIPS Code | County Seat | Est. | Population | Area (sq mi) | Area (km2) |
|---|---|---|---|---|---|---|---|
| 1 | Adair County | 1 | Kirksville | 1841 | 25,607 | 568 | 1,471 |
| 2 | Andrew County | 3 | Savannah | 1841 | 17,291 | 435 | 1,127 |
| 3 | Atchison County | 5 | Rock Port | 1843 | 5,685 | 545 | 1,412 |
| 4 | Audrain County | 7 | Mexico | 1831 | 25,529 | 693 | 1,795 |
| 5 | Barry County | 9 | Cassville | 1835 | 35,597 | 779 | 2,018 |
| 6 | Barton County | 11 | Lamar | 1855 | 12,402 | 594 | 1,538 |
| 7 | Bates County | 13 | Butler | 1841 | 17,049 | 848 | 2,196 |
| 8 | Benton County | 15 | Warsaw | 1835 | 19,056 | 706 | 1,829 |
| 9 | Bollinger County | 17 | Marble Hill | 1851 | 12,363 | 621 | 1,608 |
| 10 | Boone County | 19 | Columbia | 1820 | 162,642 | 685 | 1,774 |
| 11 | Buchanan County | 21 | Saint Joseph | 1838 | 89,201 | 410 | 1,062 |
| 12 | Butler County | 23 | Poplar Bluff | 1849 | 42,794 | 698 | 1,808 |
| 13 | Caldwell County | 25 | Kingston | 1836 | 9,424 | 429 | 1,111 |
| 14 | Callaway County | 27 | Fulton | 1821 | 44,332 | 839 | 2,173 |
| 15 | Camden County | 29 | Camdenton | 1841 | 44,002 | 655 | 1,696 |
| 16 | Cape Girardeau County | 31 | Jackson | 1812 | 75,674 | 579 | 1,500 |
| 17 | Carroll County | 33 | Carrollton | 1833 | 9,295 | 695 | 1,800 |
| 18 | Carter County | 35 | Van Buren | 1859 | 6,265 | 508 | 1,316 |
| 19 | Cass County | 37 | Harrisonville | 1833 | 99,478 | 699 | 1,810 |
| 20 | Cedar County | 39 | Stockton | 1845 | 13,982 | 476 | 1,233 |
| 21 | Chariton County | 41 | Keytesville | 1821 | 7,831 | 756 | 1,958 |
| 22 | Christian County | 43 | Ozark | 1859 | 77,422 | 563 | 1,458 |
| 23 | Clark County | 45 | Kahoka | 1836 | 7,139 | 507 | 1,313 |
| 24 | Clay County | 47 | Liberty | 1822 | 221,939 | 396 | 1,026 |
| 25 | Clinton County | 49 | Plattsburg | 1833 | 20,743 | 419 | 1,085 |
| 26 | Cole County | 51 | Jefferson City | 1820 | 75,990 | 392 | 1,015 |
| 27 | Cooper County | 53 | Boonville | 1818 | 17,601 | 565 | 1,463 |
| 28 | Crawford County | 55 | Steelville | 1829 | 24,696 | 743 | 1,924 |
| 29 | Dade County | 57 | Greenfield | 1841 | 7,883 | 490 | 1,269 |
| 30 | Dallas County | 59 | Buffalo | 1841 | 16,777 | 542 | 1,404 |
| 31 | Daviess County | 61 | Gallatin | 1836 | 8,433 | 567 | 1,469 |
| 32 | DeKalb County | 63 | Maysville | 1843 | 12,892 | 424 | 1,098 |
| 33 | Dent County | 65 | Salem | 1851 | 15,657 | 754 | 1,953 |
| 34 | Douglas County | 67 | Ava | 1857 | 13,684 | 815 | 2,111 |
| 35 | Dunklin County | 69 | Kennett | 1843 | 31,953 | 546 | 1,414 |
| 36 | Franklin County | 71 | Union | 1818 | 101,492 | 922 | 2,388 |
| 37 | Gasconade County | 73 | Hermann | 1821 | 15,222 | 520 | 1,347 |
| 38 | Gentry County | 75 | Albany | 1841 | 6,738 | 492 | 1,274 |
| 39 | Greene County | 77 | Springfield | 1833 | 275,174 | 675 | 1,748 |
| 40 | Grundy County | 79 | Trenton | 1839 | 10,261 | 436 | 1,129 |
| 41 | Harrison County | 81 | Bethany | 1843 | 8,957 | 725 | 1,878 |
| 42 | Henry County | 83 | Clinton | 1834 | 22,272 | 702 | 1,818 |
| 43 | Hickory County | 85 | Hermitage | 1845 | 9,627 | 399 | 1,033 |
| 44 | Holt County | 87 | Oregon | 1841 | 4,912 | 462 | 1,197 |
| 45 | Howard County | 89 | Fayette | 1816 | 10,144 | 466 | 1,207 |
| 46 | Howell County | 91 | West Plains | 1857 | 40,400 | 928 | 2,404 |
| 47 | Iron County | 93 | Ironton | 1857 | 10,630 | 551 | 1,427 |
| 48 | Jackson County | 95 | Independence | 1826 | 674,158 | 605 | 1,567 |
| 49 | Jasper County | 97 | Carthage | 1841 | 117,404 | 640 | 1,658 |
| 50 | Jefferson County | 99 | Hillsboro | 1818 | 218,733 | 657 | 1,702 |
| 51 | Johnson County | 101 | Warrensburg | 1834 | 52,595 | 831 | 2,152 |
| 52 | Knox County | 103 | Edina | 1843 | 4,131 | 506 | 1,311 |
| 53 | Laclede County | 105 | Lebanon | 1849 | 35,571 | 766 | 1,984 |
| 54 | Lafayette County | 107 | Lexington | 1821 | 33,381 | 629 | 1,629 |
| 55 | Lawrence County | 109 | Mount Vernon | 1843 | 38,634 | 613 | 1,588 |
| 56 | Lewis County | 111 | Monticello | 1833 | 10,211 | 505 | 1,308 |
| 57 | Lincoln County | 113 | Troy | 1818 | 52,566 | 630 | 1,632 |
| 58 | Linn County | 115 | Linneus | 1837 | 12,761 | 620 | 1,606 |
| 59 | Livingston County | 117 | Chillicothe | 1837 | 15,195 | 535 | 1,386 |
| 60 | Macon County | 121 | Macon | 1837 | 15,566 | 804 | 2,082 |
| 61 | Madison County | 123 | Fredericktown | 1818 | 12,226 | 497 | 1,287 |
| 62 | Maries County | 125 | Vienna | 1855 | 9,176 | 528 | 1,368 |
| 63 | Marion County | 127 | Palmyra | 1826 | 28,781 | 438 | 1,134 |
| 64 | McDonald County | 119 | Pineville | 1847 | 23,083 | 540 | 1,399 |
| 65 | Mercer County | 129 | Princeton | 1845 | 3,785 | 454 | 1,176 |
| 66 | Miller County | 131 | Tuscumbia | 1837 | 24,748 | 592 | 1,533 |
| 67 | Mississippi County | 133 | Charleston | 1842 | 14,358 | 413 | 1,070 |
| 68 | Moniteau County | 135 | California | 1845 | 15,607 | 417 | 1,080 |
| 69 | Monroe County | 137 | Paris | 1831 | 8,840 | 646 | 1,673 |
| 70 | Montgomery County | 139 | Montgomery City | 1818 | 12,236 | 539 | 1,396 |
| 71 | Morgan County | 141 | Versailles | 1833 | 20,565 | 598 | 1,549 |
| 72 | New Madrid County | 143 | New Madrid | 1812 | 18,956 | 678 | 1,756 |
| 73 | Newton County | 145 | Neosho | 1838 | 58,114 | 626 | 1,621 |
| 74 | Nodaway County | 147 | Maryville | 1843 | 23,370 | 877 | 2,271 |
| 75 | Oregon County | 149 | Alton | 1841 | 10,881 | 792 | 2,051 |
| 76 | Osage County | 151 | Linn | 1841 | 13,878 | 606 | 1,570 |
| 77 | Ozark County | 153 | Gainesville | 1841 | 9,723 | 747 | 1,935 |
| 78 | Pemiscot County | 155 | Caruthersville | 1851 | 18,296 | 493 | 1,277 |
| 79 | Perry County | 157 | Perryville | 1821 | 18,971 | 475 | 1,230 |
| 80 | Pettis County | 159 | Sedalia | 1833 | 42,201 | 685 | 1,774 |
| 81 | Phelps County | 161 | Rolla | 1857 | 45,156 | 673 | 1,743 |
| 82 | Pike County | 163 | Bowling Green | 1818 | 18,516 | 673 | 1,743 |
| 83 | Platte County | 165 | Platte City | 1838 | 89,322 | 420 | 1,088 |
| 84 | Polk County | 167 | Bolivar | 1835 | 31,137 | 637 | 1,650 |
| 85 | Pulaski County | 169 | Waynesville | 1833 | 52,274 | 547 | 1,417 |
| 86 | Putnam County | 171 | Unionville | 1843 | 4,979 | 518 | 1,342 |
| 87 | Ralls County | 173 | New London | 1821 | 10,167 | 471 | 1,220 |
| 88 | Randolph County | 175 | Huntsville | 1829 | 25,414 | 482 | 1,248 |
| 89 | Ray County | 177 | Richmond | 1820 | 23,494 | 570 | 1,476 |
| 90 | Reynolds County | 179 | Centerville | 1845 | 6,696 | 811 | 2,100 |
| 91 | Ripley County | 181 | Doniphan | 1831 | 14,100 | 630 | 1,632 |
| 92 | Saint Charles County | 183 | Saint Charles | 1812 | 360,485 | 561 | 1,453 |
| 93 | Saint Clair County | 185 | Osceola | 1841 | 9,805 | 677 | 1,753 |
| 94 | Saint Francois County | 187 | Farmington | 1821 | 65,359 | 450 | 1,165 |
| 95 | Saint Louis County | 189 | Clayton | 1812 | 1,000,438 | 508 | 1,316 |
| 96 | Saint Louis City | 510 | St. Louis | 1876 | 319,294 | 61.9 | 160 |
| 97 | Ste. Genevieve County | 186 | Ste. Genevieve | 1812 | 18,145 | 502 | 1,300 |
| 98 | Saline County | 195 | Marshall | 1820 | 23,370 | 756 | 1,958 |
| 99 | Schuyler County | 197 | Lancaster | 1843 | 4,431 | 308 | 798 |
| 100 | Scotland County | 199 | Memphis | 1841 | 4,843 | 438 | 1,134 |
| 101 | Scott County | 201 | Benton | 1822 | 39,191 | 421 | 1,090 |
| 102 | Shannon County | 203 | Eminence | 1837 | 8,441 | 1,004 | 2,600 |
| 103 | Shelby County | 205 | Shelbyville | 1835 | 6,373 | 501 | 1,298 |
| 104 | Stoddard County | 207 | Bloomfield | 1835 | 29,968 | 827 | 2,142 |
| 105 | Stone County | 209 | Galena | 1851 | 32,202 | 463 | 1,199 |
| 106 | Sullivan County | 211 | Milan | 1843 | 6,714 | 651 | 1,686 |
| 107 | Taney County | 213 | Forsyth | 1837 | 51,675 | 632 | 1,637 |
| 108 | Texas County | 215 | Houston | 1843 | 26,008 | 1,179 | 3,054 |
| 109 | Vernon County | 217 | Nevada | 1851 | 21,159 | 834 | 2,160 |
| 110 | Warren County | 219 | Warrenton | 1833 | 32,513 | 432 | 1,119 |
| 111 | Washington County | 221 | Potosi | 1813 | 25,195 | 760 | 1,968 |
| 112 | Wayne County | 223 | Greenville | 1818 | 13,521 | 761 | 1,971 |
| 113 | Webster County | 225 | Marshfield | 1855 | 36,202 | 593 | 1,536 |
| 114 | Worth County | 227 | Grant City | 1861 | 2,171 | 266 | 689 |
| 115 | Wright County | 229 | Hartville | 1841 | 18,815 | 682 | 1,766 |
