The double valley separating Raccoon Mountain, on the northwest, from Lookout and Chandler Mountains, on the southeast. It consists of two parts—one called Big Wills Valley, which is much the larger and includes all the valley drained by Big Wills Creek; the other called Little Wills Valley, being that part between East Red Mountain and Lookout Mountain, drained by Little Wills Creek. Together the valleys extend from the Georgia line southwestward through DeKalb and Etowah Counties for a distance of about 70 miles, and have an average width of nearly 5 miles, making their combined area approximately 350 square miles. The central portion of Wills Valley is composed of a broken belt of cherty hills and ridges. Its geological formations are the lower Silurian, Pelham (Trenton) limestones and siliceous (Knox) dolomite and chert; the Devonian black shale; the lower Subcarboniferous, Fort Payne chert; and the upper Subcarboniferous, Bangor limestones and Hartselle sandstones.