The Smoky Hills are an upland region of hills in the central Great Plains of North America. They are located in the Midwestern United States, encompassing north-central Kansas and a small portion of south-central Nebraska. The hills are a dissected plain covered by tallgrass and mixed-grass prairie. The Smoky Hills were formed by erosion of sedimentary deposits from the Cretaceous period and expose chalk, limestone, and sandstone rock outcroppings.