Devil's Slide earned its name. This 600-foot stretch of Highway 1 between Pacifica and Montara traversed an actively sliding coastal cliff, and it closed repeatedly -- sometimes for months at a stretch -- when sections of roadbed slipped into the Pacific. A five-month closure in January 1995 was the breaking point, bringing national attention to a problem that had plagued coastal travelers since the highway was first routed along the slide in 1937. Before that, the old Pedro Mountain Road crossed the ridge above, with grades as steep as 25 percent. A short railroad tunnel had been built through the area by the Ocean Shore Railroad in 1908, but it was destroyed during Prohibition to prevent bootleggers from using it.

California first proposed bypassing Devil's Slide in 1958, with an inland route called the Martini Creek Bypass. The route bisected McNee Ranch State Park and drew fierce opposition. By 1975, 55 percent of the right-of-way had been acquired before work was abandoned. The Sierra Club proposed a tunnel alternative in 1973. Caltrans studied it in 1974 and concluded it was viable, then dropped the idea. In 1985, Caltrans revived the freeway bypass. The Sierra Club sued, citing California law restricting Highway 1 to two lanes in rural areas. The discovery of Caltrans's cost-manipulation documents in 1995 finally shifted the political calculus. On November 5, 1996, San Mateo County voters approved Measure T, and nine days later Caltrans reversed its position.

Ground was broken on May 6, 2005. Boring of the twin 30-foot-diameter tunnels began on September 17, 2007. The northbound bore is 4,149 feet long, the southbound 4,008 feet -- making them the second and third longest road tunnels in California, just behind the Wawona Tunnel in Yosemite. Breakthrough on the northern bore came on September 30, 2010. When the tunnels opened in 2013, the old Devil's Slide highway was converted into a pedestrian and bicycle trail, preserving the dramatic cliff-edge views without the danger of driving them. The tunnels are named for Congressman Tom Lantos, who secured federal funding for the project, though most locals simply call them the Devil's Slide tunnels.