The original highway was promoted by lawyer and entrepreneur Sam Hill and engineer Samuel C. Lancaster, to be modeled after the great scenic roads of Europe. From the very beginning, the roadway was envisioned not just as means of traveling by the then popular Model T, but designed with an elegance that took full advantage of all the natural beauty along the route.
When the United States highway system was officially established in 1926, the highway became the part of U.S. Route 30. Since then, modern Interstate 84 has been built parallel to the highway between Portland and The Dalles, replacing it as the main travel route and resulting in the loss of some of the original sections of road.
The eventual highway was primarily designed by engineer and landscape architect Samuel C. Lancaster, a lifelong friend of good roads promoter Samuel Hill. His first contribution to the Pacific Northwest was as a consultant for Seattle's Olmsted boulevard system, part of its preparations for the 1909 Alaska-Yukon-Pacific Exposition. In 1908, the two traveled to Europe for the First International Road Congress, where Hill represented the state of Washington. Hill was especially impressed by Switzerland's Axenstrasse, a road built along Lake Lucerne in 1865 that included a windowed tunnel, and wanted to build a similar scenic highway through the Columbia River Gorge. With Lancaster's help, Hill built the experimental Maryhill Loops Road from the river east of the gorge up the Columbia Hills to his planned Quaker utopian community at Maryhill. The road was the first asphalt road in the state, designed with gradual horseshoe curves to avoid steep grades. However, Washington's lawmakers denied his request for a cross-state trunk route on the river's north bank, and Hill crossed the river to Oregon, the last of the states in the far Western U.S. to create a highway department. With the help of his life-size model at Maryhill, he convinced the state legislature to create the State Highway Commission in 1913, which would work with the counties to build roads. The Multnomah County commissioners agreed later that year that the state should design the route to distance it from county politics, and set aside an initial $75,000.
In laying out the highway, Lancaster sought not only to create a transportation artery, but to make the gorge's "beautiful waterfalls, canyons, cliffs and mountain domes" accessible to "men from all climes". According to locating engineer John Arthur Elliott, Lancaster began surveying near the Chanticleer Inn, where Larch Mountain Road, part of Multnomah County's existing road network, began climbing the hills of the gorge. For five months, from September 1913 to January 1914, he laid out a route for about 21 miles (34 km) to the Hood River County line west of Cascade Locks. The alignment generally had a maximum grade of 5% and curve radius of 200 feet (60 m), and was wide enough for 18 feet (5.5 m) of macadam (later asphalt) and two 3-foot (1 m) gravel shoulders. To accomplish this, Lancaster used curves similar to the road he had designed at Maryhill where the highway descended from Crown Point.
To carry rainwater off the road, Lancaster designed a comprehensive drainage system, including raising the center of the road, installing concrete curbs and gutters as on a city street, and taking the road over heavy flows on culverts. Eleven larger reinforced concrete bridges and several full or half viaducts were specially designed for the Multnomah County portion of the highway, taking the road over streams or along steep hillsides with a minimum of earthmoving. Masonry was used for retaining walls, which kept the highway from falling off the hillside, and guard walls, which kept drivers and pedestrians from falling off the road. At Oneonta Bluff, the highway passed through the first of five tunnels, as the land to the north was taken by the rail line. With the completion of the Oneonta Tunnel and a number of bridges, the road was open to traffic west of Warrendale, near Horsetail Falls, by October 1914. In April 1915, Multnomah County voters approved the cost of covering the initial macadam with a patented long-lasting bituminous mixture known as Warrenite, which was completed to the county line by the end of the summer.
For the section west of the Chanticleer Inn, Multnomah County generally made improvements to existing roads. Base Line Road (Stark Street) stretched east from Portland almost to the Sandy River; the roadway east of Troutdale Road to the river, including the present Sweetbriar Road, was somewhat circuitous. An old wooden Pratt through truss bridge over the Sandy collapsed on April 25, 1914, and its steel replacement was built as part of the Columbia River Highway project. A new extension of Base Line Road, built in 1915, gradually descended the riverbank to the bridge. Between the river and the inn, existing roads were incorporated into the highway, which bypassed other sections such as Neilson Road and Bell Road. The county built a second approach to the highway in 1916, using the existing Sandy Boulevard to Troutdale and a 1912 through truss bridge that connected to Woodard Road. A new roadway bypassed Woodard Road's steep grades, following the riverbank to the east end of the 1914 bridge. The entire length of the highway in Multnomah County was maintained by the county until January 16, 1930, when the state took over maintenance of the Sandy Boulevard route. (Stark Street was never a state-maintained highway, though for a time it was signed as U.S. Route 30 Alternate.)
Beyond Multnomah County, State Highway Department engineer John Arthur Elliott surveyed a route along the river through Hood River County in 1913 and 1914, mostly using the 1870s wagon road where available. County voters approved a bond issue in mid-1914 to pay for construction west of the city of Hood River, helped by highway promoter Simon Benson's purchase of the entire issue and promise to pay any overruns. The most difficult location was at Mitchell Point, where the old road included grades of up to 23% to take it over a saddle, and the railroad occupied the only available land between the cliff and the river. Elliott solved the problem by building the Mitchell Point Tunnel - a windowed tunnel like on Switzerland's Axenstrasse - through the cliff, with a viaduct on the west approach. Construction began in March 1915, and the Mitchell Point section was opened to traffic in early September, at a cost of about $47,000. To dedicate the completed highway between Portland and Hood River, two ceremonies were held at Multnomah Falls and Crown Point on the same day in June 1916.
Between Hood River and The Dalles, construction was delayed by rugged terrain west of and debate over the best route east of Mosier. Elliott considered several options west of Mosier, including a route close to the railroad, which had again taken the best location along the river, and a route over the Mosier Hills, closer to the existing county road (now Old Dalles Drive and Hood River Road). The former, while shorter, would be, in Elliott's words, "passing a section made up of views which would leave a lasting impression on the traveler". Elliott had left the State Highway Department by 1917, when new locating engineer Roy A. Klein surveyed a third alignment. It was closer to the river than the old county road, yet higher than Elliott's river alignment, in order to avoid closing the rail line during blasting. Just after leaving Hood River on a 1918 bridge over the Hood River, which had replaced an older wooden truss bridge, the highway climbed via a series of loops, similar to the ones at Crown Point. From there it followed the course of the river, partway up the hillside. Near the east end, the Mosier Twin Tunnels, completed in 1920, carried the road through a portion of the hill; the eastern of the two included two windows, similar to the five at Mitchell Point.
The final piece to The Dalles was laid out by J. H. Scott of the State Highway Department. It followed an inland route, climbing existing county roads to the Rowena Crest, where it used a third set of loops to descend to river level at Rowena. There it picked up a former alignment of the Oregon-Washington Railroad and Navigation Company most of the way to The Dalles. Most of the bridges in Wasco County were designed by Conde McCullough, who would later become famous for his work on U.S. Route 101, the Oregon Coast Highway. A completion ceremony for the Columbia River Highway was held on June 27, 1922, when Simon Benson symbolically helped pave the final portion near Rowena. By then, the roadway was part of a longer Columbia River Highway, stretching from Astoria on the Pacific Ocean east to Pendleton as Highway No. 2 in a large network of state highways. In the State Highway Department's fifth biennial report, published in 1922, it reported that construction costs to date on the Columbia River Highway totaled about $11 million, with the state contributing $7.6 million, the federal government $1.1 million, and the counties $2.3 million ($1.5 million of which was from Multnomah County). In 1926, the American Association of State Highway Officials designated the road as part of U.S. Route 30. The first realignment was made by 1935 at the west entrance to The Dalles, where a more direct route along West 2nd Street bypassed the old alignment along West 6th Street, the Mill Creek Bridge, and West 3rd Place.
Even as construction was ongoing on the east end of the Columbia River Highway, the design had become obsolete, as motorists wanting to get to their destination greatly outnumbered tourists taking a pleasure drive. There were also problems with rockfall, especially west of the Mosier Twin Tunnels. By 1932, Lancaster proposed a new water-level route, while keeping the old road as a scenic highway. The first such bypass was necessitated by the federal government's creation of Bonneville Dam on the Columbia River. The dam would flood the railroad, and the highway would need to be moved so the railroad could take its place. The highway's new two-lane alignment, completed in 1937, crossed the old road several times between the community of Bonneville (just east of Tanner Creek) and Cascade Locks. The realignment had the effect of closing the old road to all but the most local of traffic, since the construction of the east portal of the new Toothrock Tunnel, just west of a new bridge over Eagle Creek, had destroyed a section of road on the hillside.
By the end of the 1940s, the original cross section of 18 feet (5.5 m) of pavement and two 3-foot (1 m) shoulders had been modified to 24 feet (7.5 m) of pavement. The Mosier Twin Tunnels were similarly widened from 8⅔ feet (2⅔ m) to 10 feet (3 m) in each direction in 1938 to accommodate larger trucks, but this was not enough, and traffic signals were later installed at the tunnels to regulate one-way traffic. A 1948 bypass of the Oneonta Tunnel was made possible by moving the railroad slightly north on fill; the railroad benefited by removing the risk of the thin tunnel wall collapsing onto the track.
More comprehensive bypass planning began by 1941, when the State Highway Commission adopted surveys for the new highway.
Modern highways, including I-84, and other developments have resulted in the abandonment of major sections of the historic original highway. In the interest of tourism and historical preservation, seventy-four miles of the original road—from Troutdale to The Dalles—have been established as the Historic Columbia River Highway (HCRH). Forty miles of the route are open to motor vehicles:
The remaining portions of the HCRH designated for non-motorized use are now known as the Historic Columbia River Highway State Trail. These are being developed as money becomes available. Roughly seven miles between Hood River and Mosier have been open to non-motorized traffic since 2000, passing through the historic Mosier Tunnels.
Once restoration is complete, the highway will serve as a scenic and alternative bicycle route for I-84 and US 30 between The Dalles and Portland. Currently, cyclists wishing to travel between these two towns must ride on the shoulders of I-84 for much of the distance, or the much more dangerous and narrow State Route 14 on the Washington side of the river.
The Columbia River Highway is the nation's oldest scenic highway. In 1984 it was recognized as a National Historic Civil Engineering Landmark by the American Society of Civil Engineers. In 2000 it was designated a National Historic Landmark by the National Park Service as "an outstanding example of modern highway development".