Lafayette County is a county in the western portion of Missouri, part of the Kansas City metropolitan area. As of the 2020 census, the population was 32,984. Its county seat is Lexington. The county was organized November 16, 1820, from Cooper County and originally named Lillard County for James Lillard of Tennessee, who served in the first state constitutional convention and first state legislature. It was renamed Lafayette County on February 16, 1825, in honor of Revolutionary War hero the Marquis de La Fayette, who was then visiting the United States.

Saline County is located along the Missouri River in the U.S. state of Missouri. As of the 2020 census, the population was 23,333. Its county seat is Marshall. The county was established November 25, 1820, and named for the region's salt springs.