As one of the Columbia River's two main tributaries that drain north central Oregon, the John Day River flows westward from the Blue Mountains and then north through deeply dissected country. In draining some 8,000 square miles, the John Day Basin also exhibits impressive relief. Ranging from several hundred to more than two thousand feet above the streams, a number of ridges dominate this region. Valleys separating the ridges usually have sloping sides, such that their floors are rarely flat and usually somewhat narrow.
This drainage basin is classified as being within the Blue Mountains physiographic (landform) province of Oregon.  It is also a borderland between two larger provinces--the Columbia Plateau and the Basin and Range--which are part of a broader categorization scheme used for North America. The Columbia Plateau covers about 100,000 square miles to the north and west of the John Day Basin, and consists largely of flat or gently tilted basaltic flows. South and east of the basin is the Basin and Range Province which features a wide variety of rock types that are folded or faulted. Local separation of the two provinces is provided by the Strawberry and Aldrich mountains along the south side of the John Day River valley. 
Juniper and sage dominate the upland areas and characterize semi-arid conditions throughout the basin, where average annual precipitation is just 13 inches.  Some contrast to the sparse cover at lower elevations is, however, provided by the riparian areas that support comparatively lush vegetation, as well as by plant communities associated with pine forests above 5,000 feet in elevation. Most of the upper basin is too dry and rugged for extensive cultivation. Cropping is restricted to riverine areas that can be irrigated. Livestock grazing remains the basin's main industry, with human settlement sparse compared to more temperate parts of Oregon.
As representative of the wider basin, John Day Fossil Beds National Monument consists of 14,400 acres in three noncontiguous units. Sheep Rock is the largest unit, located a few miles northwest of Dayville in Grant County. The next biggest unit is Painted Hills, lying 10 miles northwest of Mitchell in adjacent Wheeler County. Also in Wheeler County is the smallest unit, Clarno, roughly 20 miles southwest of Fossil. An administrative headquarters is located at the park's main visitor contact point, that being the Cant Ranch in the Sheep Rock Unit.
Last Updated: 30-Apr-2002