This region of Kansas contains the Smoky Hills, an area of rolling hills, occasional mesas, and buttes, with striking outcroppings. Pawnee Rock, Coronado Heights, and Rock City are notable Dakota sandstone formations in this region. The Smoky Hills Region features sandstone caps in the east such as the rock "toadstools" in this park. More of these unique forms, sculpted by erosion, may be seen at Mushroom Rocks State Park near Carneiro, east of Ellsworth. In the mid-section of the region, hills are capped with limestone. Because of the scarcity of wood, early settlers made stone fence posts from this limestone. This custom is still in use. Chalk outcroppings can be seen in the western part of the region. Castle Rock and Monument Rocks are large chalk formations found in Gove County. Chalk bluffs are also located in Logan and Trego counties. These chalk formations, such as Wildcat Canyon in Trego County, are excellent sources of fossils from the Cretaceous Era.