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Iron Mountain Road, Black Hills, South Dakota
Photo: KimonBerlin · CC BY-SA 2.0

Drives South Dakota The Black Hills and the Badlands

Iron Mountain Road

Iron Mountain Road, US 16A · Custer State Park → Keystone

Intense17.1 mi45 min2,400 ft climbHigh point ≈ 5,400 ftOne way
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The drive

Iron Mountain Road is the 17-mile stretch of US 16A from Custer State Park to Keystone. Peter Norbeck, a former South Dakota governor, helped lay it out as a slow, scenic drive for tourists, and a memorial to him stands at the summit of Iron Mountain.

The road is known for pigtail bridges, including one at the exit of a tunnel, and for single-lane tunnels that frame the faces on Mount Rushmore. The three tunnels are the Doane Robinson (12 feet wide, 11 feet 4 inches high), the C.C. Gideon (11 feet 6 inches wide, 10 feet 9 inches high) and the Scovel Johnson (10 feet 9 inches wide, 11 feet high).

Along the way

  1. Custer State Park (Highway 36 junction)
  2. Iron Mountain
  3. Doane Robinson Tunnel
  4. Keystone
Elevation
2,400 ft of climbing · high point ≈ 5,400 ft
Custer State ParkKeystone
Curves
Twisty most of the way
Custer State ParkKeystone
GentleHairpins

Good to know

  • Custer State Park advises driving no more than 20 mph on this road.
  • The tunnels are narrow: the narrowest, the Scovel Johnson, is 10 feet 9 inches wide.
  • The road closes periodically in winter, depending on conditions and how quickly it can be cleared.
  • Vehicles traveling non-stop through Custer State Park on US 16A do not need a park pass.

Open all year, weather permitting. Roads close for snow, fire, storms and repairs: before you set off, check South Dakota 511.

Questions about this drive

How long does Iron Mountain Road take?

Iron Mountain Road from Custer State Park to Keystone is 17.1 miles and takes about 45 minutes.

Is Iron Mountain Road open in winter?

It closes periodically in winter, depending on conditions and how quickly the road can be cleared safely.

How wide are the tunnels on Iron Mountain Road?

The Doane Robinson Tunnel is 12 feet wide, the C.C. Gideon 11 feet 6 inches and the Scovel Johnson 10 feet 9 inches.

Do I need a Custer State Park pass for Iron Mountain Road?

Vehicles traveling non-stop through the park on US 16A don't need one, according to the park's website.

What you get in the app

Turn by turn, on this roadSpoken directions along the exact route. Carve never reroutes you onto a faster one.
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Distance, time, elevation, curves and intensity are from Carve's route. Checked 2026-10-28.

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Map of Iron Mountain Road, from Custer State Park to Keystone