Painted Hills is one of the three units of the John Day Fossil Beds National Monument, located in Wheeler County, Oregon.It totals 3,132 acres (1,267 ha) and is located 9 miles (14 km) northwest of Mitchell, 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 floodplain.
The black soil is lignite that was vegetative matter that grew along the floodplain. The grey coloring is mudstone, siltstone, and shale.The red coloring is laterite soil that formed by floodplain deposits when the area was warm and humid.
An abundance of fossil remains of early horses, camels, and rhinoceroses in the Painted Hills unit makes the area particularly important to vertebrate paleontologists