Drumheller Channels National Natural Landmark in south-central Washington preserves the Columbia Plateau’s most significant basalt butte-and-basin channeled scablands, a vast maze of dry channels, rock basins, potholes, and steep-sided buttes shaped by Ice Age floods. Its form reflects changes in the ancient Columbia River’s course during the late Pleistocene after glacial ice blocked older routes, and later Missoula floodwaters rushed south through this broad erosional cascade along Crab Creek. Designated in 1986 for both scenic and scientific importance, the area also reflects later human impacts from overgrazing and irrigation and now supports extensive wetlands and abundant wildlife within and near regional refuge lands.