John Day Fossil Beds National Monument is a U.S. National Monument in Wheeler and Grant counties in east-central Oregon. Located within the John Day River basin and managed by the National Park Service, the park is known for its well-preserved layers of fossil plants and mammals that lived in the region between the late Eocene, about 44 million years ago, and the late Miocene, about 7 million years ago. The monument consists of three geographically separate units: Sheep Rock, Painted Hills, and Clarno. The units cover a total of 13,944 acres (5,643 ha) of semi-desert shrublands, riparian zones, and colorful badlands. About 125,000 people visit the park each year for outdoor activities such as hiking and sightseeing or to visit the Thomas Condon Paleontology Center or the James Cant Ranch Historic District. Before the arrival of Euro-Americans in the 19th century, the John Day basin was frequented by Sahaptin people who hunted, fished, and gathered roots and berries in the region. After road-building made the valley more accessible, settlers established farms, ranches, and a few small towns along the river and its tributaries. Paleontologists have been unearthing and studying the fossils in the region since 1864, when Thomas Condon, a missionary and amateur geologist, recognized their importance and made them known globally. Parts of the basin became a National Monument in 1975.