Missouri counties on the Missouri River

St. Louis (saynt LOO-iss, sənt-) is an independent city in the U.S. state of Missouri. It is located near the confluence of the Mississippi and the Missouri rivers. In 2020, the city proper had a population of 301,578, while its metropolitan area, which extends into Illinois, had an estimated population of over 2.8 million. It is the largest metropolitan area in Missouri and the second-largest in Illinois. The city's combined statistical area is the 20th-largest in the United States.

Holt County is a county located in the northwestern portion of the U.S. state of Missouri. As of the 2020 census, the population was 4,223. Its county seat is Oregon. The county was organized February 15, 1841. Originally named Nodaway County, it was soon renamed for David Rice Holt (1803–1840), a Missouri state legislator from Platte County.

Jackson County is located in the western portion of the U.S. state of Missouri, on the border with Kansas. As of the 2020 census, the population was 717,204. making it the second-most populous county in the state (after St. Louis County in the east). Although Independence retains its status as the original county seat, Kansas City, Missouri, serves as a second county seat and the center of county government. The county was organized December 15, 1826, and named for former Tennessee senator Andrew Jackson, who would become President of the United States three years later in 1829.

St. Louis County is located in eastern Missouri. It is bounded by the City of St. Louis and the Mississippi River to the east, the Missouri River to the north, and the Meramec River to the south. At the 2020 census, the total population was 1,004,125, making it the most populous county in Missouri. Its county seat is Clayton. The county is included in the St. Louis, MO–IL metropolitan statistical area.

Andrew County is a county located in the northwestern part of the U.S. state of Missouri. As of the 2020 census, the county had a population of 18,135. Its county seat is Savannah. The county was organized January 29, 1841, and named for Andrew Jackson Davis, a lawyer and prominent citizen of St. Louis.

Boone County is located in the U.S. state of Missouri. Centrally located the state's Mid-Missouri region, its county seat is in Columbia, which is Missouri's fourth-largest city and location of the University of Missouri. As of the 2020 U.S. Census, the county's population was listed as 183,610, making it the state's eighth-most populous county. The county was organized November 16, 1820, removed from the former larger Howard County (now to the northwest) of the old federal Missouri Territory of 1812-1821, and named for the famous Western explorer and settler of Kentucky, then recently deceased Daniel Boone (1734-1820), whose kin largely populated the Boonslick area, having arrived in the 1810s on the Boone's Lick Road.

Buchanan County is located in the U.S. state of Missouri. As of the 2020 United States Census, the population was 84,793. Its county seat is St. Joseph. When originally formed in 1838, the county was named Roberts County, after settler Hiram Roberts. It was renamed in 1839 for James Buchanan, then a U.S. Senator and later President of the United States. The county was formed from land annexed to Missouri, as were five other counties. Buchanan County is included in the Kansas City CSA.

Callaway County is a county located in the U.S. state of Missouri. As of the 2020 United States Census, the county's population was 44,283. Its county seat is Fulton. With a border formed by the Missouri River, the county was organized November 25, 1820, and named for Captain James Callaway, grandson of Daniel Boone. The county has been historically referred to as "The Kingdom of Callaway" after an incident in which some residents confronted Union troops during the U.S. Civil War.

Chariton County is a county located in the north-central portion of the U.S. state of Missouri. As of the 2020 census, the population was 7,408. Its county seat is Keytesville. The county was organized November 16, 1820, from part of Howard County and is named for the Chariton River.

Cole County is located in the central part of the U.S. state of Missouri. As of the 2020 census, its population was 77,279. Its county seat and largest city is Jefferson City, the state capital. The county was organized November 16, 1820, and named after pioneer William Temple Cole who built Cole's Fort in Boonville.