Carved directly through a narrow granite spire in the Black Hills, the Needles Eye Tunnel stands as one of South Dakota’s most distinctive engineering feats. Completed in 1922 as part of the Needles Highway (SD 87), the one-lane tunnel measures just 8 feet 4 inches wide and 11 feet 3 inches high, requiring careful navigation by passing vehicles. Its name comes from the adjacent rock formation, where centuries of wind and water erosion sculpted a sharp, needle-like opening. Surrounded by dense ponderosa pine forest and sheer stone walls, this section of the highway offers one of the most dramatic mountain drives in the American Midwest, linking the spire formations of Custer State Park with the scenic byways leading toward Sylvan Lake and Mount Rushmore.

The Needles of the Black Hills of South Dakota are a region of eroded granite pillars, towers, and spires within Custer State Park. Popular with rock climbers and tourists alike, the Needles are accessed from the Needles Highway, which is a part of Sylvan Lake Road (SD 87/89). The Cathedral Spires and Limber Pine Natural Area, a 637-acre portion of the Needles containing six ridges of pillars as well as a disjunct stand of limber pine, was designated a National Natural Landmark in 1976. -- Wikipedia