Devils Den is a boulder-strewn Gettysburg Battlefield hill used by artillery and infantry (e.g., snipers) during the 1863 Battle of Gettysburg, Second Day. A visitor attraction since the memorial association era, several boulders are worn from foot traffic and the site includes numerous cannon, memorials, and walkways, including a bridge spanning 2 boulders.
Devils Den was formed with Little Round Top (to the east-northeast) and Big Round Top (southwest) by periglacial frost wedging of the igneous landform formed 200 million years ago when the "outcrop of the Gettysburg sill" intruded through the Triassic "Gettysburg plain".:13 After c. 1855, for 25 years through 1881, a 15 ft (4.6 m) snake had been reported between the Emmitsburg Road & Devils Den, and the 1898 black snake had a length of only 8 ft (2.4 m). Named before the battle, some soldiers' accounts used the name "Devil's Cave", and a depression on a boulder that collects water resembles a flying horned bat.
The 124th NY monument with Ellis statue was dedicated near Devil's Den in 1884. Postbellum avenues were constructed to Devil's Den such as Sickles' Avenue from the west, Crawford Avenue in 1895 (north),:'95 and Warren Avenue across Plum Run (east). From 1894-1916, the Gettysburg Electric Railway operated on a curve crossing Plum Run (Rock Creek) around the south base of the hill with the Tipton Station providing Devil's Den services. In 1916, a Devil's Den boulder was used as a Satterlee Hospital memorial at Philadelphia's Clark Park.
The nearby 1933 comfort station was demolished in 2009, and its access bridge over Plum Run remains to the east. In 1952, ROTC students conducted a mock battle at the site, and the "Devil's Den Access Committee" was formed in 1988. The site's ID Tablet was designated a Historic District Contributing Structure in 2004, and the Devil's Den barricade is structure WA35 on the Gettysburg National Military Park's List of Classified Structures.