Clay County, MO
Clay County is sometimes known as 'Little Dixie'. Named for Henry Clay, former Senator and United States Secretary of State, Clay County was established on January 2, 1822. Located in western Missouri, it covers an area of 409 mi². With a population of 246,365, it is the fifth most populous county in Missouri. The county seat is located in Liberty, which was named after the Declaration of Independence.
Greene County, MO
Greene County is located in southwestern Missouri and encompasses 678 mi². It's the fourth most populous county in the state with a population of 291,293. The county seat is located in Springfield, the “Birthplace of Route 66". Established on January 2, 1833, the county was named for Nathaneal Greene - a general from the American Revolutionary War.
Jackson County, MO
Jackson County was named for former U.S. President Andrew Jackson. It's has area of 616 mi² and a population of 700,307. The county seat is located in Independence, known as “Queen City of the Trails”. Jackson County was established on December 15, 1826.
St. Charles County, MO
St. Charles County was named for Italian cardinal Saint Charles Borromeo. It's located in eastern Missouri, covering an area of 593 mi². Established in 1812, the county seat is located in St. Charles, the ninth largest city in Missouri. St. Charles is the third most populous county in the state and, as of the 2018 census, has a population of 399,182.
St. Louis County, MO
St. Louis County was originally under French rule, but was brought under U.S. control after the Louisiana Purchase. Located in eastern Missouri, it covers an area of 523 mi². The most populous county in the state, it has an estimated population of 996,945. Established as a county on October 1, 1812, the city of Clayton has served as county seat since 1877.