 Boonville was named the county seat in 1818.The community's position on the Santa Fe Trail and Missouri River led to many historically important residents during the era of westward expansion, including politicians William Ash (a former slave turned Virginia General Assemblyman), David Barton, George Graham Vest (famous for his "man’s best friend" closing argument in an 1869 trial), and self-taught artist George Caleb Bingham.The Cooper County Jail was built in 1848 and remained in place until 1979 with a claim that it was the longest-serving jail in Missouri history.