For countless hundreds of years along the Red River, periodic flooding washed trees and brush from the soft soil along the banks and into the river. Eventually this formed the biggest logjam the world has ever seen. The native Caddo tribes said the wide river had always been covered with this logjam. They couldn’t imagine the river, or life, without it. At its peak in the 1830s, this heap of dead, tangled trees stretched off and on for more than 160 miles. They called it “The Great Raft.” To open navigation on the Red River, the US Army Corps of…