Withrow Moraine and Jameson Lake Drumlin Field erosion resulting from the Missoula Floods, which laid bare many layers of the basalt flows on the edges of the plateau at Grand Coulee and Moses Coulee. Two million years ago the Pleistocene epoch began and Ice age glaciers invaded the area. They scoured the Columbia River Plateau, reaching as far south as the middle of the Waterville Plateau highlands above the Grand Coulee and south to the head of Moses Coulee. In some areas north of the Grand Coulee they were as much as 3 km (10000 feet) thick. Grooves in the exposed granite bedrock are still visible in
Coulee City, Washington Coulee City, Washington Coulee City is a town in Grant County, Washington. The population was 562 at the 2010 census. The town was named after nearby Grand Coulee. Coulee City was officially incorporated on May 10, 1907. Coulee City is located at (47.611942, -119.290904). According to the United States Census Bureau, the town has a total area of , all of it land. As of the census of 2010, there were 562 people, 265 households, and 150 families residing in the town. The population density was . There were 331 housing units at an average density of . The racial