Cooper County administrative offices are located at 200 Main Street, Boonville, MO 65233; phone: 660-882-2114.
Two years after the organization of Howard County the immigration began to flow so steadily that there was great demand for the division of Howard County and for the formation of another county south of the Missouri River. Yielding to and in compliance with this demand the territorial Legislature, on December 17, 1818, formed the new county of Cooper which included all of Howard County south of the Missouri River and the Osage River extending westwardly to the western territorial boundary. Able Owens, William Wear, Charles Canole, Luke Williams and Julius Emmons were appointed commissioners to locate the county seat. The county was named for Sarshel (Benjamin) Cooper, an early pioneer in the territory. This territory embraced what would become 11 entire counties and parts of 5 other counties. Various reorganizations ultimately settled the boundaries of Cooper County in 1845.