The Columbia River Scenic Highway, built over a 10-year period (1913-1922) at the beginning of the automobile age, was an engineering and civic achievement of its time. Most of the major engineering features originally built on the highway still exist, including 17 bridges, seven viaducts, three tunnels, long stretches of dry masonry retaining walls, rustic parapets, and pedestrian overlooks. Before a citizens' committee became involved in the preservation of the original highway and its related structures, seven original bridges and a tunnel were destroyed. The original Columbia River Highway fell into disrepair and was neglected for 40 years. In 1981 an inventory by the National Park Service of the original highway and its associated resources led to a renewed commitment by national, state, and local governments and citizens to restore it to its original integrity. As a result of the highway being listed on the National Register of Historic Places in 1981, national and state legislation has been passed to protect the highway as a historic resource for future generations to enjoy.