- Adair
- Est: Jan 29, 1841
- County Seat: Kirksville
- Post Offices
- Andrew
- Est: Jan 29, 1841
- County Seat: Savannah
- Post Offices
- Atchison
- Est: Feb 14, 1845
- County Seat: Rockport
- Post Offices
- Audrain
- Est: Dec 17, 1836
- County Seat: Mexico
- Post Offices
- Barry
- Est: Jan 5, 1835
- County Seat: Cassville
- Post Offices
- Barton
- Est: Dec 12, 1855
- County Seat: Lamar
- Post Offices
- Bates
- Est: Jan 29, 1841
- County Seat: Butler
- Post Offices
- Benton
- Est: Jan 3, 1835
- County Seat: Warsaw
- Post Offices
- Bollinger
- Est: Mar 1, 1851
- County Seat: Marble Hill
- Post Offices
- Boone
- Est: Jan 1, 1821
- County Seat: Columbia
- Post Offices
- Buchanan
- Est: Dec 31, 1838
- County Seat: Saint Joseph
- Post Offices
- Butler
- Est: Feb 27, 1849
- County Seat: Poplar Bluff
- Post Offices
- Caldwell
- Est: Dec 29, 1836
- County Seat: Kingston
- Post Offices
- Callaway
- Est: Nov 25, 1820
- County Seat: Fulton
- Post Offices
- Researcher(s):
- Camden
- Est: Jan 29, 1841
- County Seat: Camdenton
- Post Offices
- Cape Girardeau
- Est: Oct 1, 1812
- County Seat: Jackson
- Post Offices
- Carroll
- Est: Jan 2, 1833
- County Seat: Carrollton
- Post Offices
- Carter
- Est: Mar 10, 1859
- County Seat: Van Buren
- Post Offices
- Cass
- Est: Mar 3, 1835
- County Seat: Harrisonville
- Post Offices
- Cedar
- Est: Feb 14, 1845
- County Seat: Stockton
- Post Offices
- Chariton
- Est: Jan 1, 1821
- County Seat: Keytesville
- Post Offices
- Christian
- Est: Mar 8, 1859
- County Seat: Ozark
- Post Offices
- Clark
- Est: Dec 16, 1836
- County Seat: Kahoka
- Post Offices
- Clay
- Est: Jan 2, 1822
- County Seat: Liberty
- Post Offices
- Clinton
- Est: Jan 2, 1833
- County Seat: Plattsburg
- Post Offices
- Cole
- Est: Jan 1, 1821
- County Seat: Jefferson City
- Post Offices
- Cooper
- Est: Feb 1, 1819
- County Seat: Boonville
- Post Offices
- Crawford
- Est: Jan 23, 1829
- County Seat: Steelville
- Post Offices
- Dade
- Est: Jan 29, 1841
- County Seat: Greenfield
- Post Offices
- Dallas
- Est: Jan 29, 1841
- County Seat: Buffalo
- Post Offices
- Daviess
- Est: Dec 29, 1836
- County Seat: Gallatin
- Post Offices
- De Kalb
- Est: Feb 25, 1845
- County Seat: Maysville
- Post Offices
- De Witt
- Name given to area later Pulaski County
- Limited P.O. info listed
- Dent
- Est: Feb 10, 1851
- County Seat: Salem
- Post Offices
- Dodge
- Now in Iowa, included Putnam County area
- Limited P.O. info listed
- Douglas
- Est: Oct 29, 1857
- County Seat: Ava
- Post Offices
- Dunklin
- Est: Feb 14, 1845
- County Seat: Kennett
- Post Offices
- Franklin
- Est: Jan 1, 1819
- County Seat: Union
- Post Offices
- Gasconade
- Est: Jan 1, 1821
- County Seat: Hermann
- Post Offices
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- Gentry
- Est: Feb 14, 1845
- County Seat: Albany
- Post Offices
- Greene
- Est: Jan 2, 1833
- County Seat: Springfield
- Post Offices
- Grundy
- Est: Jan 29, 1841
- County Seat: Trenton
- Post Offices
- Harrison
- Est: Feb 14, 1845
- County Seat: Bethany
- Post Offices
- Researcher(s):
- Henry
- Est: Dec 13, 1834
- County Seat: Clinton
- Post Offices
- Hickory
- Est: Feb 14, 1845
- County Seat: Hermitage
- Post Offices
- Holt
- Est: Jan 29, 1841
- County Seat: Oregon
- Post Offices
- Howard
- Est: Mar 1, 1816
- County Seat: Fayette
- Post Offices
- Howell
- Est: Mar 2, 1857
- County Seat: West Plains
- Post Offices
- Iron
- Est: Feb 17, 1857
- County Seat: Ironton
- Post Offices
- Jackson
- Est: Dec 15, 1826
- County Seat: Independence
- Post Offices
- Jasper
- Est: Jan 29, 1841
- County Seat: Carthage
- Post Offices
- Jefferson
- Est: Jan 1, 1819
- County Seat: Hillsboro
- Post Offices
- Johnson
- Est: Dec 13, 1834
- County Seat: Warrensburg
- Post Offices
- Knox
- Est: Feb 14, 1845
- County Seat: Edina
- Post Offices
- Laclede
- Est: Feb 24, 1849
- County Seat: Lebanon
- Post Offices
- Lafayette
- Est: Jan 1, 1821
- County Seat: Lexington
- Post Offices
- Lawrence
- Est: Feb 14, 1845
- County Seat: Mount Vernon
- Post Offices
- Lewis
- Est: Jan 2, 1833
- County Seat: Monticello
- Post Offices
- Lincoln
- Est: Jan 1, 1819
- County Seat: Troy
- Post Offices
- Linn
- Est: Jan 6, 1837
- County Seat: Linneus
- Post Offices
- Livingston
- Est: Jan 6, 1837
- County Seat: Chillicothe
- Post Offices
- Macon
- Est: Jan 6, 1837
- County Seat: Macon
- Post Offices
- Madison
- Est: Jan 1, 1819
- County Seat: Fredericktown
- Post Offices
- Maries
- Est: Mar 2, 1855
- County Seat: Vienna
- Post Offices
- Marion
- Est: Dec 23, 1826
- County Seat: Palmyra
- Post Offices
- Mc Donald
- Est: Mar 3, 1849
- County Seat: Pineville
- Post Offices
- Researcher(s):
- Mercer
- Est: Feb 14, 1845
- County Seat: Princeton
- Post Offices
- Miller
- Est: Feb 6, 1837
- County Seat: Tuscumbia
- Post Offices
- Mississippi
- Est: Feb 14, 1845
- County Seat: Charleston
- Post Offices
- Moniteau
- Est: Feb 14, 1845
- County Seat: California
- Post Offices
- Monroe
- Est: Jan 6, 1831
- County Seat: Paris
- Post Offices
- Montgomery
- Est: Jan 1, 1819
- County Seat: Montgomery City
- Post Offices
- Morgan
- Est: Jan 5, 1833
- County Seat: Versailles
- Post Offices
- New Madrid
- Est: Oct 1, 1812
- County Seat: New Madrid
- Post Offices
- Newton
- Est: Dec 31, 1838
- County Seat: Neosho
- Post Offices
- Niangua
- Name chg’d to Dallas
- Limited P.O. info listed
- Nodaway
- Est: Feb 14, 1845
- County Seat: Maryville
- Post Offices
- Oregon
- Est: Feb 14, 1845
- County Seat: Alton
- Post Offices
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- Osage
- Est: Jan 29, 1841
- County Seat: Linn
- Post Offices
- Ozark
- Est: Jan 29, 1841
- County Seat: Gainesville
- Post Offices
- Pemiscot
- Est: Feb 19, 1851
- County Seat: Caruthersville
- Post Offices
- Perry
- Est: Jan 1, 1821
- County Seat: Perryville
- Post Offices
- Pettis
- Est: Jan 26, 1833
- County Seat: Sedalia
- Post Offices
- Phelps
- Est: Nov 13, 1857
- County Seat: Rolla
- Post Offices
- Pike
- Est: Feb 1, 1819
- County Seat: Bowling Green
- Post Offices
- Platte
- Est: Dec 31, 1838
- County Seat: Platte City
- Post Offices
- Polk
- Est: Jan 5, 1835
- County Seat: Bolivar
- Post Offices
- Pulaski
- Est: Jan 19, 1833
- County Seat: Waynesville
- Post Offices
- Putnam
- Est: Feb 28, 1845
- County Seat: Unionville
- Post Offices
- Ralls
- Est: Jan 1, 1821
- County Seat: New London
- Post Offices
- Randolph
- Est: Jan 23, 1829
- County Seat: Huntsville
- Post Offices
- Ray
- Est: Jan 1, 1821
- County Seat: Richmond
- Post Offices
- Reynolds
- Est: Feb 25, 1845
- County Seat: Centerville
- Post Offices
- Ripley
- Est: Jan 5, 1833
- County Seat: Doniphan
- Post Offices
- Rives
- Name chg'd to Henry
- Limited P.O. info listed
- Saint Charles
- Est: Oct 1, 1812
- County Seat: Saint Charles
- Post Offices
- Saint Clair
- Est: Jan 29, 1841
- County Seat: Osceola
- Post Offices
- Saint Francois
- Est: Dec 19, 1821
- County Seat: Farmington
- Post Offices
- Saint Louis
- Est: Oct 1, 1812
- County Seat: Clayton
- Post Offices
- Saint Louis (City)
- Est: Oct 1, 1876
- County Seat: Saint Louis
- Post Offices
- Saline
- Est: Jan 1, 1821
- County Seat: Marshall
- Post Offices
- Schuyler
- Est: Feb 14, 1845
- County Seat: Lancaster
- Post Offices
- Scotland
- Est: Jan 29, 1841
- County Seat: Memphis
- Post Offices
- Scott
- Est: Mar 1, 1822
- County Seat: Benton
- Post Offices
- Shannon
- Est: Jan 29, 1841
- County Seat: Eminence
- Post Offices
- Shelby
- Est: Jan 2, 1835
- County Seat: Shelbyville
- Post Offices
- Ste. Genevieve
- Est: Oct 1, 1812
- County Seat: Ste. Genevieve
- Post Offices
- Stoddard
- Est: Jan 2, 1835
- County Seat: Bloomfield
- Post Offices
- Stone
- Est: Feb 10, 1851
- County Seat: Galena
- Post Offices
- Sullivan
- Est: Feb 14, 1845
- County Seat: Milan
- Post Offices
- Taney
- Est: Jan 6, 1837
- County Seat: Forsyth
- Post Offices
- Texas
- Est: Feb 14, 1845
- County Seat: Houston
- Post Offices
- Van Buren
- Name chg'd to Cass
- Limited P.O. info listed
- Vernon
- Est: Feb 27, 1855
- County Seat: Nevada
- Post Offices
- Warren
- Est: Jan 5, 1833
- County Seat: Warrenton
- Post Offices
- Researcher(s):
- Washington
- Est: Nov 1, 1813
- County Seat: Potosi
- Post Offices
- Wayne
- Est: Feb 1, 1819
- County Seat: Greenville
- Post Offices
- Webster
- Est: Mar 3, 1855
- County Seat: Marshfield
- Post Offices
- Worth
- Est: Feb 25, 1861
- County Seat: Grant City
- Post Offices
- Wright
- Est: Jan 29, 1841
- County Seat: Hartville
- Post Offices
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