Iron Mountain Road (US-16A)

Engineered to slow you down, not speed you through. Iron Mountain Road — 17 miles, 314 curves, 14 switchbacks, three pigtail bridges that loop the road over itself to manage steep elevation gain, and three tunnels boresighted to frame Mount Rushmore like a gun sight. Constructed in 1933 to connect Custer State Park and Mount Rushmore while holding traffic to 35 miles per hour, it links two of the Black Hills' most visited destinations by the most deliberate route imaginable. The tunnel views work in one direction only; drive it both ways.