Remains of the Imperial Dunes Plank Road
Winterhaven, California
It was bad enough crossing the Imperial Valley sand dunes of Southern California on horseback. Early automobiles found it impossible. So in 1916, a one-lane road of wooden planks was laid across the eight miles of sand, funded almost entirely by the far-away city of San Diego, which wanted to lure people from the East by the most direct route. The speed limit was 10 mph. If there was a lot of traffic, traveling the eight miles could take up to two days.
The plank road -- the original Route 80 -- lasted for a dozen years until it was replaced by an asphalt road and then today's four-lane highway. It still crosses the dunes in spots, and a surviving section (with its own historical marker) can be seen from a roadside picnic area at Grays Wells. But you'd be nuts to try to drive on it.