In the early 1930’s, Los Angeles County began construction of an additional roadway over the San Gabriel Mountains via the East Fork of the San Gabriel River. The road, then known as the Camp Bonita – Prairie Fork Road, was about half complete with with four larger bridges and a tunnel, by early 1938. Work had progressed as far as “The Narrows” by 1938. However, the March 2-3, 1938 storms caused much of the roadway to be washed out. The project was then abandoned, leaving a large arch bridge stranded many miles upriver. The tunnel still exists as well, just north of the “Bridge to Nowhere”, though it has been sealed at both ends.

In the 1955,  a new road building project commenced in the canyon, first known as East Fork Road, then Shoemaker Canyon Road. This new alignment would stay high above the canyon floor until it got nearer to the “Bridge to Nowhere”, allowing that earlier work to come to some use. Progress on this roadway was slow, mostly due to poor funding. Convict labor was used for most of the project, similar to many other road building efforts at the time in Los Angeles County. Two tunnels were constructed as well. These still exist and are mostly intact. This project too was cancelled in 1976 , leaving another large scar in the canyon. This road is presently known as Shoemaker Canyon Road.

Today, the canyon is protected from future development through the Sheep Mountain Wilderness Area. Even without this protection, the geology of the canyon makes for a very expensive project. Maintenance would also be costly, as seen with State 39 through San Gabriel Canyon and above Crystal Lake. In time, all these structures and cuts will wash away, leaving the canyon with only bits of concrete and asphalt to show what was once here.