| County | Contact | Est | County Seat | Origin |
| Adair County | Adopt Me! | 1841 | Kirksville | Macon County |
| Andrew County | Adopt Me! | 1841 | Savannah | Part of the Platte Purchase |
| Atchison County | Adopt Me! | 1843 | Rock Port | Holt County, part of the Platte Purchase |
| Audrain County | Adopt Me! | 1831 | Mexico | Callaway, Monroe and Ralls counties |
| Barry County | Adopt Me! | 1835 | Cassville | Greene County |
| Barton County | Adopt Me! | 1855 | Lamar | Jasper County |
| Bates County | Sheryl McClure | 1841 | Butler | Van Buren (now Cass) County |
| Benton County | Adopt Me! | 1835 | Warsaw | Pettis and Greene counties |
| Bollinger County | Adopt Me! | 1851 | Marble Hill | Cape Girardeau, Madison, Stoddard and Wayne counties |
| Boone County | Adopt Me! | 1821 | Columbia | Howard County |
| Buchanan County | Debby Moulden-Frerichs | 1838 | Saint Joseph | Part of the Platte Purchase |
| Butler County | Adopt Me! | 1849 | Poplar Bluff | Wayne County |
| Caldwell County | Adopt Me! | 1836 | Kingston | Ray County |
| Callaway County | Judy | 1821 | Fulton | Boone, Howard and Montgomery counties |
| Camden County | Adopt Me! | 1841 | Camdenton | Benton, Morgan and Pulaski counties |
| Cape Girardeau County | Adopt Me! | 1812 | Jackson | One of the five original counties |
| Carroll County | Adopt Me! | 1833 | Carrollton | Ray County |
| Carter County | John R. Baker | 1859 | Van Buren | Oregon, Reynolds, Ripley and Shannon counties |
| Cass County | Adopt Me! | 1833 | Harrisonville | Jackson County |
| Cedar County | Adopt Me! | 1845 | Stockton | Dade and St. Clair counties |
| Chariton County | Judy | 1821 | Keytesville | Howard County |
| Christian County | Adopt Me! | 1859 | Ozark | Greene, Taney and Webster counties |
| Clark County | Judy | 1836 | Kahoka | Lewis County |
Clay County  | Judy White | 1822 | Liberty | Ray County |
| Clinton County | Adopt Me! | 1833 | Plattsburg | Clay County |
| Cole County | Adopt Me! | 1820 | Jefferson City | Cooper County |
| Cooper County | Adopt Me! | 1818 | Boonville | Howard County |
| Crawford County | Adopt Me! | 1829 | Steelville | Gasconade County |
| Dade County | Adopt Me! | 1841 | Greenfield | Barry and Polk counties |
| Dallas County | Adopt Me! | 1841 | Buffalo | Polk County |
| Daviess County | Adopt Me! | 1836 | Gallatin | Ray County |
| DeKalb County | Adopt Me! | 1843 | Maysville | Clinton County |
| Dent County | Glenda Cashmer | 1851 | Salem | Crawford and Shannon counties |
| Douglas County | Adopt Me! | 1857 | Ava | Ozark County |
| Dunklin County | Adopt Me! | 1843 | Kennett | Stoddard County |
| Franklin County | Adopt Me! | 1818 | Union | St. Louis County |
| Gasconade County | Adopt Me! | 1821 | Hermann | Franklin County |
| Gentry County | Adopt Me! | 1841 | Albany | Clinton County |
| Greene County | Adopt Me! | 1833 | Springfield | Crawford and Wayne counties |
| Grundy County | Adopt Me! | 1839 | Trenton | Livingston County |
| Harrison County | Judy White | 1843 | Bethany | Daviess County |
| Henry County | Adopt Me! | 1834 | Clinton | Lillard (now Lafayette) County |
| Hickory County | Adopt Me! | 1845 | Hermitage | Benton and Polk counties |
| Holt County | Adopt Me! | 1841 | Oregon | Part of the Platte Purchase |
| Howard County | Judy | 1816 | Fayette | St. Charles and St. Louis counties |
| Howell County | Adopt Me! | 1857 | West Plains | Oregon County |
| Iron County | Adopt Me! | 1857 | Ironton | Madison, Reynolds, St. Francois, Washington & Wayne counties |
| Iron County | John R. Baker | 1857 | Ironton | Madison, Reynolds, St. Francois, Washington & Wayne counties |
| Jackson County | Adopt Me! | 1826 | Kansas City & Independence | Lillard (now Lafayette) County |
| Jasper County | Redgie Peck | 1841 | Independence & Carthage | Barry County |
| Jefferson County | Adopt Me! | 1818 | Hillsboro | St. Louis and Sainte Genevieve counties |
| Johnson County | Adopt Me! | 1834 | Warrensburg | Lillard (now Lafayette) County |
| Knox County | Adopt Me! | 1843 | Edina | Scotland County |
| Laclede County | Adopt Me! | 1849 | Lebanon | Camden, Pulaski and Wright counties |
| Lafayette County | Adopt Me! | 1821 | Lexington | Cooper County |
| Lawrence County | Adopt Me! | 1843 | Mount Vernon | Barry and Dade counties |
| Lewis County | Adopt Me! | 1833 | Monticello | Marion County |
| Lincoln County | Adopt Me! | 1818 | Troy | St. Charles County |
| Linn County | Adopt Me! | 1837 | Linneus | Chariton County |
| Livingston County | Adopt Me! | 1837 | Chillicothe | Carroll County |
| Macon County | Adopt Me! | 1837 | Macon | Chariton and Randolph counties |
| Madison County | Adopt Me! | 1818 | Fredericktown | Cape Girardeau and Sainte Genevieve counties |
| Maries County | Adopt Me! | 1855 | Vienna | Osage and Pulaski counties |
| Marion County | Judy | 1826 | Palmyra | Ralls County |
| McDonald County | Adopt Me! | 1847 | Pineville | Newton County |
| Mercer County | Adopt Me! | 1845 | Princeton | Grundy County |
| Miller County | Adopt Me! | 1837 | Tuscumbia | Cole and Pulaski counties |
| Mississippi County | Adopt Me! | 1842 | Charleston | Scott County |
| Moniteau County | Adopt Me! | 1845 | California | Cole and Morgan counties |
| Monroe County | Judy | 1831 | Paris | Ralls County |
| Montgomery County | Judy | 1818 | Montgomery City | St. Charles County |
| Morgan County | Laurie Biswell | 1833 | Versailles | Cooper County |
| New Madrid County | Adopt Me! | 1812 | New Madrid | One of the five original counties |
| Newton County | Adopt Me! | 1838 | Neosho | Barry County |
| Nodaway County | Adopt Me! | 1843 | Maryville | Andrew County, the Platte Purchase |
| Oregon County | P. J. Franklin | 1841 | Alton | Ripley County |
| Osage County | Adopt Me! | 1841 | Linn | Gasconade County |
| Ozark County | Adopt Me! | 1841 | Gainesville | Taney County |
| Pemiscot County | Adopt Me! | 1851 | Caruthersville | New Madrid County |
| Perry County | Adopt Me! | 1821 | Perryville | Sainte Geneviere County |
| Pettis County | Adopt Me! | 1833 | Sedalia | Cooper and Saline counties |
| Phelps County | Adopt Me! | 1857 | Rolla | Crawford County |
| Pike County | Judy | 1818 | Bowling Green | St. Charles County |
| Platte County | Adopt Me! | 1838 | Platte City | Part of the Platte Purchase |
| Polk County | Sheryl McClure | 1835 | Bolivar | Greene County |
| Pulaski County | Adopt Me! | 1833 | Waynesville | Crawford County |
| Putnam County | Sheryl McClure | 1843 | Unionville | Adair and Sullivan counties |
| Ralls County | Judy | 1821 | New London | Pike County |
| Randolph County | Judy | 1829 | Huntsville | Chariton and Ralls counties |
| Ray County | Adopt Me! | 1820 | Richmond | Howard County |
| Reynolds County | John R. Baker | 1845 | Centerville | Shannon County |
| Ripley County | Adopt Me! | 1831 | Doniphan | Wayne County |
| Saint Charles County | Judy | 1812 | Saint Charles | One of the five original counties |
| Saint Clair County | Adopt Me! | 1841 | Osceola | Rives (now Henry) County |
| Saint Francois County | Adopt Me! | 1821 | Farmington | Jefferson, Ste. Genevieve and Washington counties |
| Saint Louis City | Scott K. Williams | 1876 | St. Louis | Created in 1876 when city residents voted to secede from St. Louis County |
| Saint Louis County | Adopt Me! | 1812 | Clayton | One of the five original counties |
| Saline County | Adopt Me! | 1820 | Marshall | Cooper County |
| Schuyler County | Adopt Me! | 1843 | Lancaster | Adair County |
| Scotland County | Judy | 1841 | Memphis | Clark, Lewis, and Shelby counties |
| Scott County | Adopt Me! | 1822 | Benton | New Madrid County |
| Shannon County | Adopt Me! | 1837 | Eminence | Ripley County |
| Shelby County | Judy | 1835 | Shelbyville | Marion County |
| Ste. Genevieve County | Adopt Me! | 1812 | Ste. Genevieve | One of the five original counties |
| Stoddard County | Adopt Me! | 1835 | Bloomfield | New Madrid County |
| Stone County | Adopt Me! | 1851 | Galena | Taney County |
| Sullivan County | Judy | 1843 | Milan | Linn County |
| Taney County | Adopt Me! | 1837 | Forsyth | Greene County |
| Texas County | Adopt Me! | 1843 | Houston | Shannon and Wright counties |
| Vernon County | Sheryl McClure | 1851 | Nevada | Bates County |
| Warren County | Adopt Me! | 1833 | Warrenton | Montgomery County |
| Washington County | Adopt Me! | 1813 | Potosi | Sainte Genevieve County |
| Wayne County | Adopt Me! | 1818 | Greenville | Cape Girardeau and Lawrence counties |
| Webster County | Adopt Me! | 1855 | Marshfield | Greene County |
| Worth County | Adopt Me! | 1861 | Grant City | Gentry County |
| Wright County | Adopt Me! | 1841 | Hartville | Pulaski County |
