Kansas's Smoky Hills Region contains rolling hills, occasional mesas, buttes, and striking outcroppings. Notable Dakota sandstone formations in the region include Pawnee Rock, Coronado Heights, and Rock City. In the eastern part of the region, sandstone caps form features such as the rock toadstools in this park, and more erosion-sculpted forms can be seen at Mushroom Rocks State Park near Carneiro, east of Ellsworth. In the middle of the region, hills are capped with limestone, and because wood was scarce, early settlers made stone fence posts from this limestone, a custom still in use. In the western part of the region, chalk outcroppings include large formations such as Castle Rock and Monument Rocks in Gove County, along with chalk bluffs in Logan and Trego counties. These chalk formations, including Wildcat Canyon in Trego County, are excellent sources of fossils from the Cretaceous Era.