Painted Hills is one of the three units of the John Day Fossil Beds National Monument, located in Wheeler County, Oregon. Painted Hills is named after the colorful layers of its hills corresponding to various geological eras, formed when the area was an ancient river flood plain. The black soil is lignite that was vegetative matter that grew along the flood plain. The grey coloring is mudstone, silt stone, and shale. The red coloring is laterite soil that formed by flood plain deposits when the area was warm and humid.