CountyFormedParent CountySibling Counties
1Cape Girardeau County1812 Oct 01Missouri TerritoryBollinger 1851, Wayne 1818, Madison 1818
1St. Louis County1812 Oct 01Missouri TerritoryFranklin 1818, Howard 1816, Jefferson 1818, St. Louis City 1816
1St. Charles County1812 Oct 01Missouri TerritoryHoward 1816, Lincoln 1818, Pike 1818, Montgomery 1818
1Ste. Genevieve County1812 Oct 01Missouri TerritoryJefferson 1818, Madison 1818, Perry 1820, St. Francois 1821, Washington 1813
1New Madrid County1812 Oct 01Missouri TerritoryPemiscot 1851, Scott 1821, Stoddard 1835
6Washington County1813 Aug 21Ste. GenevieveIron 1857, St. Francois 1821
7Saint Louis City1816 Jan 18St. Louis ( County)
8Howard County1816 Jan 23St. Louis, St. CharlesBarry 1836, Boone 1820, Calloway 1820, Chariton 1820, Cooper 1818, Ray 1820
9Franklin County1818 Oct 11Saint LouisGasconade 1820
10Jefferson County1818 Dec 08Ste. Genevieve, St. LouisSt. Francois 1821
10Wayne County1818 Dec 11Cape Girardeau, LawrenceBollinger 1851, Butler 1849, Greene 1833, Iron 1857, Ripley 1833
11Pike County1818 Dec 14St. CharlesAdurain 1836, Ralls 1820
11Madison County1818 Dec 14Ste. Genevieve, Cape GirardeauBollinger 1851, Iron 1857
11Montgomery County1818 Dec 14St. CharlesCallaway 1820, Warren 1833
11Lincoln County1818 Dec 14Saint Charles
15Pulaski County1818 Dec 15CrawfordCamden 1841, Laclede 1849, Maries 1855, Miller 1837, Wright 1841
17Cooper County1818 Dec 17HowardBates 1841, Benton 1833, Cole 1820, Morgan 1833, Pettis 1833, Saline 1820
18Ralls County1820 Nov 16PikeAudrain 1836, Marion 1822, Monroe 1831, Randolph 1829
18Ray County1820 Nov 16HowardCaldwell 1836, Carroll 1833, Clay 1822, Clinton 1833, Daviess 1836, Grundy 1841, Harrison 1845
18Boone County1820 Nov 16HowardCallaway 1820
18Lafayette County1820 Nov 16DadeHenry 1834, Jackson 1826, Johnson 1834
18Chariton County1820 Nov 16HowardLinn 1837, Macon 1837, Randolph 1829
18Perry County1820 Nov 16Ste. Genevieve
18Atchison County1820 Nov 16Platte Purchaseoriginally named Allen until 1845
25Cole County1820 Nov 20CooperMiller 1837, Moniteau 1845
26Callaway County1820 Nov 25Howard, Boone, MontgomeryAudrain 1836
26Gasconade County1820 Nov 25FranklinCrawford 1829, Osage 1841
26Saline County1820 Nov 25CooperPettis 1833
29Saint Francois County1821 Dec 19Ste. Genevieve, JeffersonIron 1837
30Scott County1821 Dec 28New MadridMississippi 1845
31Clay County1822 Jan 02RayClinton 1833
32Marion County1822 Dec 14RallsAdair 1841, Lewis 1833, Shelby 1835
33Jackson County1826 Dec 15LafayetteCass 1835
34Randolph County1829 Jan 22Chariton, RallsMacon 1837
35Crawford County1829 Jan 23GasconadeDent 1851, Greene 1833, Phelps 1857, Pulaski 1818
36Monroe County1831 Jan 06Ralls
37Greene County1833 Jan 02Wayne, CrawfordChristian 1859, Polk 1837, Taney 1837, Webster 1855
37Lewis County1833 Jan 02MarionClark 1836, Scotland 1841
39Benton County1833 Jan 03CooperCamden 1841, Hickory 1845
39Carroll County1833 Jan 03RayLivingston 1837
41Morgan County1833 Jan 05CooperCamden 1841, Moniteau 1845
41Ripley County1833 Jan 05WayneCarter 1859, Oregon 1845, Shannon 1841
41Warren County1833 Jan 05Montgomery
44Clinton County1833 Jan 15Clay, RayDeKalb 1845, Gentry 1841
45Pettis County1833 Jan 26Saline, Cooper
46Johnson County1834 Dec 13Lafayette
46Henry County1834 Dec 13Lafayetteoriginally named Rives until 1841
48Stoddard County1835 Jan 02New MadridBollinger 1851, Dunklin 1845
48Shelby County1835 Jan 02MarionScotland 1841
50Cass County1835 Sep 14Jacksonnamed Van Buren County until 1849
51Clark County1836 Jan 02LewisScotland 1841
52Barry County1836 Jan 05HowardDade 1841, Jasper 1841, Lawrence 1845, Newton 1838
53Audrain County1836 Dec 17Pike, Calloway, Ralls
54Caldwell County1836 Dec 26Ray
55Daviess County1836 Dec 29RayHarrison 1845
56Livingston County1837 Jan 06CarrollGrundy 1841, Mercer 1845
56Macon County1837 Jan 06Randolph, Chariton
56Camden County1837 Jan 06Pulaski, Morgan, Bentonrenamed Camden 1843
59Linn County1837 Jan 07CharitonPutnam 1845, Sullivan 1843
60Taney County1837 Jan 16GreeneChristian 1859, Ozark 1841, Stone 1851
61Miller County1837 Feb 06Cole, Pulaski
62Polk County1837 Mar 20Greene, LacledeDade 1841, Dallas 1841, Hickory 1845, Niangua 1841
63Platte County1838 Dec 31Platte PurchaseAndrew 1841, Buchanan 1839, Holt 1845
63Newton County1838 Dec 31BarryMcDonald 1849
65Buchanan County1839 Feb 10Platte Purchase
66Jasper County1841 Jan 29BarryBarton 1855
66Shannon County1841 Jan 29RipleyCarter 1859, Dent 1851, Reynolds 1845, Texas 1845
66Dade County1841 Jan 29Polk, BarryCedar 1845, Lafayette 1820, Lillard 1820
66Scotland County1841 Jan 29Clark, Lewis, ShelbyKnox 1845
66Wright County1841 Jan 29PulaskiLaclede 1849, Texas 1845
66Osage County1841 Jan 29GasconadeMaries 1855
66Grundy County1841 Jan 29Livingston, RayMercer 1845
66Dallas County1841 Jan 29Polknamed Niangua until 1844
66Andrew County1841 Jan 29Platte PurchaseNodaway 1845
66Texas County1841 Jan 29Platte Purchaseoriginally named Ashley until 1845
66Adair County1841 Jan 29MaconPutnam 1845, Schuyler 1845
66Bates County1841 Jan 29CooperVernon 1851
78Gentry County1841 Feb 12ClintonWorth 1861
79St. Clair County1841 Feb 15HenryCedar 1845
80Sullivan County1843 Feb 17LinnPutnam 1845
81Ozark County1843 Feb 22renamed from Ozarkoriginally named Decatur until 1843
82Holt County1845 Jan 29renamed from old NodawayAtchison 1845
115Oregon1845 Feb 14RipleyCarter 1859, Howell 1857
83Cedar County1845 Feb 14Dade, Saint Clair
83Dunklin County1845 Feb 14Stoddard
83Harrison County1845 Feb 14Daviess, Ray
83Hickory County1845 Feb 14Benton, Polk
83Knox County1845 Feb 14Scotland
83Mercer County1845 Feb 14Grudny, Livingston
83Mississippi County1845 Feb 14Scott
83Moniteau County1845 Feb 14Cole, Morgan
83Schuyler County1845 Feb 14Adair
92Reynolds County1845 Feb 25ShannonCarter 1859, Iron 1857
92DeKalb County1845 Feb 25Clinton
92Lawrence County1845 Feb 25BarryWayne 1818
95Putnam County1845 Nov 16Adair, Sullivan, Linn
96Nodaway County1845 Dec 14Andrew
97Butler County1849 Feb 27Wayne
97Laclede County1849 Feb 27Pulaski, Wright, CamdenPolk 1837
99McDonald County1849 Mar 03Newton
100Dent County1851 Feb 10Shannon, Crawford
100Stone County1851 Feb 10Taney
102Pemiscot County1851 Feb 15New Madrid
103Vernon County1851 Feb 17Bates
104Bollinger County1851 Mar 01Madison, Stoddard, Cape Girardeau, Wayne
105Maries County1855 Mar 02Osage, Pulaski
106Webster County1855 Mar 03GreeneChristian 1859
107Barton County1855 Dec 12Jasper
108Iron County1857 Feb 16Madison, St. Francois, Wayne, Washington, Reynolds
109Howell County1857 Mar 02Oregon
110Douglas County1857 Oct 29Ozark
111Phelps County1857 Nov 13Crawford
112Carter County1859 Mar 13Ripley, Reynolds, Shannon, Oregon
113Christian County1859 Mar 20Taney, Greene, Webster
114Worth County1861 Feb 08Gentry