The Pawnee Buttes are two prominent buttes located within the Pawnee National Grassland in Weld County, of northeastern Colorado. Rising approximately 300 feet (91 m) above the surrounding plains, the buttes are erosional remnants left standing in isolation as the surrounding High Plains surface has gradually worn away. The lower portions of the buttes are composed of relatively soft, clay-rich sedimentary rock called the Brule formation.