Inside Iron Creek Tunnel, Custer State Park, South Dakota

Iron Creek Tunnel carries Needles Highway through a granite outcrop in Custer State Park. The road was built in the 1920s under the direction of South Dakota Governor Peter Norbeck, who laid out the route on foot and horseback to highlight the Black Hills' granite spires. Norbeck designed several tunnels along the highway to frame views of Mount Rushmore and the surrounding needle rock formations, and Iron Creek Tunnel remains one of the narrower passages on the route, cut directly through native granite rather than lined with concrete. The highway connects to the Peter Norbeck Scenic Byway, a National Scenic Byway that also links to Custer State Park's Wildlife Loop Road.