Villages on Missouri's Black River like Lesterville and Centerville used to be oases of tranquillity, the destination of weekend canoeists, tube floaters and fishermen. No longer. All too often the solitude of the Ozarks wilderness is shattered these days by the whine and rumble of powerful engines. The river's banks are littered with mountains of discarded beer cans, used Pampers and empty motor-oil cans. A steady stream of pickup trucks rolls through village streets hauling trailers loaded with all-terrain vehicles, heading for the river's edge. Locals call it "the Invasion."
On Memorial Day weekend the invaders descended with a vengeance. Each...