1879: San Mateo County builds a coastal road along Devils Slide. According to the San Mateo County Historical Association, a San Francisco newspaper provides the following description in 1912 of a drive on the Half Moon Bay-Colma Road: "As treacherous a piece of road as can be found. Death stalks in front and lurks behind in every foot of the climb to the summit."
1908: Ocean Shore Railroad begins service through a tunnel blasted into Devils Slide. The company initially planned for a top-of-the-line electric railway, but the 1906 earthquake curtailed investors' interest. The company's vision for an 80-mile railway from San Francisco to Santa Cruz was never realized.
1915: Coastside Boulevard, providing an inland route to the east of San Pedro Mountain, is completed. Farmers begin trucking their produce to markets in San Francisco using this road, reducing demand for the train.
1920: The Ocean Shore Railway ceases service. Mitch Postel, president of the San Mateo County Historical Association, said the 1906 earthquake remains a disaster that dramatically affected the coast's future development. Plans were already afoot to build communities along the line. "If it hadn't been for the earthquake, who knows?" Postel said. "It's a big question of history."
1937: Caltrans completes a 5.9-mile extension of Highway 1 traversing Devils Slide between Pacifica and Montara. It follows much of the same path as the Ocean Shore Railway.
1938: A landslide forces the first major closure of the highway at Devils Slide. There would be many slides in years to come, including in 1942, 1951, 1952, 1977, 1982, 1983, 1995 and 2006.
1950-59: By the 1950s, the road at Devils Slide had developed a reputation for danger. It was during this decade that Cal Hinton began working for the Pacifica Fire Department. He served as chief from 1970 to 1983. In his 28 years with the department, he told the historical association he worked on more than 50 incidents at Devils Slide, most of them cars off the roadway or climbers in peril. In 1955 he responded to an accident in which a San Francisco firefighter and his wife both died while driving to pick up their kids from summer camp. Children's clothing was strewed along the cliff.
1960: The California Highway Commission proposes a 7.5-mile highway of four to six lanes from Pacifica to the Half Moon Bay Airport.
1967: A San Francisco woman throws her 9- and 10-year-old children over the cliff at Devils Slide, then plunges after them to her death.
1972: The San Mateo County Board of Supervisors approves the bypass. The Sierra Club and other groups file a lawsuit against Caltrans, halting the project. They propose a tunnel, which is rejected as too expensive.
1986: The California Coastal Commission approves a shorter alternative for the bypass, a 4.5-mile version that rejoins Highway 1 near Montara. Environmental groups appeal.
1996: A study shows the tunnels can be built for $148 million. County voters overwhelmingly approve Measure T in favor of the tunnel project.
2005: Caltrans breaks ground May 26 on the first phase. By this time the project is estimated to cost $270 million.
2007: A ceremony is held Sept. 17 for the beginning of tunnel excavation.
2013: The tunnels will open to traffic in March. The tunnels feature state-of-the-art safety features, including heat and carbon monoxide sensors. Each 30-foot-wide tunnel has 16 jet fans for ventilation.