The rock shelters and the fortress-like boulder fields record a long history of human habitation and research indicates that the area may have been inhabited as many as 15,000 years ago. Archeological artifacts discovered within the park indicate that it was the site of ancient Indian burials. For centuries, the Horse Pens 40 site was variously occupied by the Creeks and Cherokees, who battled repeatedly over control of the area. The huge boulders and sheer stone walls formed a natural fortress that was valued by the occupants as protection, as a ceremonial site, and as a place to corral livestock. Local lore holds that a peace treaty between the Creeks and the Cherokees was signed on the property; the area was subsequently populated by the Cherokee until their forced removal in the "Trail of Tears." During the Civil War, Horse Pens 40 was used by locals to hide livestock, vulnerable family members, and valuables from marauding Union and Confederate soldiers. When Confederate forces eventually discovered the site, they used it to store supplies for troops operating in the area. After the war, moonshiners and bandits moved into the area, capitalizing on the remoteness and using the rock shelters as hideouts.
In the 1880s, a Georgian named John Hyatt purchased land in the area with his wife. The original deed for the land from this transfer refers to the division of the property as "the home 40, the farming 40, and the horse pens 40, each tract consisting of 40 acres of land," thus giving Horse Pens 40 its name. Descendants of the original Hyatt family still occupy nearby areas of the mountain. The land was used for livestock grazing and farming until the late 1950s.
In 1984, Musgrove closed the site and it sat dormant for 15 years, when it was purchased by a couple who intended to once again organize concerts. This plan never came to fruition, and the park was sold again in 2000. The new owner ran into financial problems, and in 2002 the park was sold to the current owners, who have promoted the park as both a music and climbing venue and added new facilities including a pavilion, country store and restaurant. Horse Pens 40 continues as a site for bluegrass music events and festivals, but the primary attraction of the park remains the unique rock formations that attract rock climbers who specialize in the form of the sport known as bouldering, which does not allow ropes or anchors. Bouldering competitions are held annually, including one leg of the Triple Crown Bouldering Series, an annual competition for world class climbers. Horse Pens 40 also is home to a variety of animals, including red and grey foxes, coyotes, raccoons, deer, flying squirrels, groundhogs, cottontail rabbits, and grey squirrels.
Amenities include eight rustic cabins, added by the current owners, which are available for rent, a primitive campground, and a picnic area with a playground for children, restrooms and shower facilities, a covered pavilion, a store that sells camping supplies and climbing equipment, and a restaurant. The park is open all year with the exception of some holidays. There is a day use fee for climbers and others. Camping fees include free climbing access.
