Coosa County was created by the Alabama legislature on 18 December 1832 from lands included in the Creek Indian Treaty of Cusseta, 1832 Mar. 24. It was named for the Coosa River, which forms its western boundary. The word "Coosa" is believed to mean "cane-brake" in the Alabama-Kossati Indian dialect. Coosa County lies in the east-central part of the state. It is bordered by Shelby, Talladega, Clay, Tallapoosa, Elmore, and Chilton counties. A site on Albert Crumpler's plantation on Hatchemalega Creek was chosen as the county seat and given the name Lexington. In 1835 the name was changed to Rockford. Other towns and communities include Equality, Nixburg, and Goodwater.
Elmore County was created by the Alabama legislature on 15 February 1866 from parts of Autauga, Coosa, Montgomery, and Tallapoosa Counties. It was named for General John Archer Elmore, a veteran of the American Revolution and early settler of Alabama. Elmore County lies in the east-central part of the state. It is drained by the Coosa and the Tallapoosa Rivers, which merge to form the Alabama River a few miles south of Wetumpka. The French established Fort Toulouse at the confluence of the Coosa and Tallapoosa in 1717, upon which site Gen. Andrew Jackson erected Fort Jackson in 1814, following the Battle of Horseshoe Bend. Wetumpka is the county seat. Other towns and communities include Eclectic, Tallassee, and Millbrook.