Attorney and entrepreneur Samuel C. Hill was a primary mover in the struggle to get a motor road built through the Cascade Mountains from Portland toward eastern Oregon. In 1906 Hill invited Samuel C. Lancaster, an engineer who had gained recognition for the design of a network of county roads in Tennessee, to the Northwest. As their acquaintance grew, Hill decided that Lancaster was the man who could design and build the highway that Hill had dreamed about. The project began with a survey in September 1913, and grading was started in October.

The best level land between the Columbia River and the base of the cliffs had been used for the railroad. This meant that the highway would have to be built up higher and in some places near or over the crest of certain promontories. This, combined with advanced design standards that met requirements to enhance the beauty of the gorge, made it a challenging project. All the bridges and viaducts were built of cast-in-place concrete. The roadbed itself was paved with asphalt and compacted stone, a mixture described at the time as bitulithic warrenite. The bridges were designed to be light, graceful, and strong. The entire scenic highway was completed in 1922.