Harney Peak is the highest mountain in South Dakota, located in Black Hills National Forest. Its elevation is 7,242 ft (2,207 m). The peak is the highest point east of the Rocky Mountains in mainland North America. 

 An abandoned fire lookout tower is situated on the summit. A plaque at the base of the tower which reads “Valentine McGillycuddy, Wasicu Wacan” marks the final resting place for Dr. Valentine McGillycuddy. The peak was named in the late 1850s by Lieutenant Gouverneur K. Warren in honor of General William S. Harney, who was commander of the military in the Black Hills area in the late 1850s. The top can be reached by following the trails either from Sylvan Lake or Horse Thief Lake. The hike from Sylvan Lake to the summit and back is about 6 miles (10 km). 

 Harney Peak is located within the Black Elk Wilderness area. No permit is required for use of the trail, although the National Forest Service asks (at a self-service kiosk) that hikers register to obtain a free permit upon entering the Black Elk Wilderness area, en route to the summit. The entire area around Harney Peak is one of the most popular hiking locations in the Black Hills. The trails which course through the Black Elk Wilderness and nearby Custer State Park are walked on at all seasons of the year.