One of our favorite activities in the Black Hills of South Dakota is to take a slow drive along the scenic Iron Mountain Highway where many of the one way tunnels form a picture frame around Mount Rushmore. I also love the unique engineering design in the pigtail bridges used in place of hair pin turns to navigate down the side of Iron Mountain.

We are camped near Custer State Park and the town of Custer in the southern part of the Black Hills at Custer's Gulch RV-Park. It is an OK commercial campground just like dozens of others in this area.

Iron Mountain Highway Scenic Drive in the Black Hills of South Dakota

I wonder how many of these hairpin turns or switchbacks there are on the Scenic Drives in the Black Hills.

Warning sign on Iron Mountain Highway in the Black Hills of South Dakota

This is one of the "big" tunnels at 10' 6" wide.

Tunnel on the Iron Mountain Highway framing Mount Rushmore in the Black Hills of South Dakota

Note that Mount Rushmore is framed in this tunnel.

Pigtail Bridge on the Iron Mountain Highway in the Black Hills of South Dakota

In order for some of those tunnel shots (of Mount Rushmore) to work many of the tunnels emerge into essentially "thin air". Road builders designed a series of pigtail bridges as a solution. Pigtail bridges perform the same function as switchbacks. They move traffic from one elevation to another as easily as possible. Since these tunnels popped out into thin air these bridges were constructed from the mouth of the tunnel and in a sweeping motion corkscrew down. This picture was taken immediately after exiting one of those tunnels. You can see how the road corkscrews around and passes under the bridge. A pretty impressive piece of engineering that I have only seen here in the Black Hills.

Pigtail bridge on the Iron Mountain Highway in the Black Hills of South Dakota

This is one of those pigtail bridges on the Iron Mountain Highway Scenic Drive. This may be the place where they string two of them together as the highway really drops in elevation.

Pigtail bridge on the Iron Mountain Highway in the Black Hills of South Dakota

Pigtail bridge helping us change elevation. Note that this pigtail bridge allows us to pass under the road we are on.

One lane tunnel on the Iron Mountain Scenic Drive in the Black Hills of South Dakota

There are a dozen or so of these one lane tunnel signs on the scenic drives in the Black Hills. Thank goodness there is not a lot of traffic.

This is a real hairpin turn sign in the Black Hills of South Dakota

This was a real "sporty" hairpin/switchback for them to reduce the speed to 5-mph.

Low Narrow Tunnel sign on Iron Mountain Highway in the Black Hills of South Dakota

This tunnel is getting a bit narrow but not as narrow as the "famous" one at the Needles.

Pigtail Bridge sign in the Black Hills of South Dakota

This is one of the pigtail bridge signs, it is a good indication things are going to happen fast.

That is all there is.