It crosses the southern Santa Lucia Range at an altitude of 1,522 feet (464 m), and connects San Luis Obispo, roughly 5 miles (8.0 km) to the south,[1] with Atascadero, Paso Robles, and the Salinas Valley to the north.

[3] The pass was long used by indigenous people,[4] and lies on the boundary between the historical homelands of the Northern Chumash and Salinans.

In 1876 the city of San Luis Obispo funded the construction of an improved and smoother stagecoach road across the pass.

[4] The construction of its original seven tunnels included the removal of a record 1.1 million cubic yards (0.84×10^6 m3) of hand-drilled rock.

[4] In 1938, the highway was realigned again, to the east side of the canyon, and widened to four lanes;[8] portions of the two older alignments can still be found.