One of the last vestiges of eastern Washington’s natural, unirrigated landscape, protected in its untrammeled splendor by the nonprofit Nature Conservancy, Moses Coulee is an 800-foot-deep gorge bounded by vertical walls of ruddy brown volcanic basalt, brightened by splashes of green and orange lichen. From the rolling plains above, US-2 cuts down into the coulee, then back up the other side, passing through some of the Columbia River Basin’s sole surviving sagebrush and giving a strong sense of how profoundly irrigation has changed the region.