Pinnacle Mountain, a 1,011-foot summit about 13 miles northwest of downtown Little Rock, is the defining feature of Pinnacle Mountain State Park and a prominent landmark across much of Pulaski County because of its steep south slopes and position near the Arkansas River. Though it can resemble a cinder cone, it is not volcanic but formed of hard Jackfork Sandstone deposited in an ancient ocean and later uplifted during the Pennsylvanian Period as Pangaea formed. Now an erosional remnant of the older Ouachita mountain system, it is also a major hiking destination, with summit and base trails drawing visitors from the Little Rock area.