According to the U.S. Census Bureau, the county has a total area of , of which is land and (0.3%) is water. The Green River forms the western boundary and Colorado lies on the eastern boundary. The Colorado River flows through the southeast corner. Deserts, cliffs and plateaus make up the scenery, with few settlements apart from the city of Moab, a Colorado River oasis. Arches National Park lies in the southern part of the county, just north of Moab. Also, the northernmost extension of Canyonlands National Park lies in the southwest corner of the county.