Created by an Act of the Legislature on December 7, 1821, Decatur County was formed from portions of Madison and Jackson Counties. "Old Woodville," two miles north along County Highway 7, was designated as the county seat. A survey completed in 1823-24 revealed that it did not contain the constitutionally required number of square miles. The county was abolished by an Act of the Legislature on December 28, 1825, and its territory was returned to Madison and Jackson Counties.