Although the pass was visited in August 1769 by Catalan explorer Gaspar de Portolá, it eventually was named for Henry Newhall, a significant businessman in the area during the 19th century.

Weather conditions in the pass can vary from triple-digit heat in the summer to rare below freezing temperatures in winter.

[1] In 1853, a Los Angeles businessman, Henry Clay Wiley, installed a windlass atop the Fremont Pass to speed and ease the ascent and descent of the steep Santa Clara Divide.

[2] The steep pass was made easier to cross when a deep slot-like road was cut through the "San Fernando Mountain" by Charles H. Brindley, Andrés Pico, and James R. Vineyard.

In return for helping tame the most daunting obstacle along the Fort Tejon Road, the main inland route from Los Angeles to the north, the State of California awarded them a twenty-year contract to maintain the turnpike and collect tolls.

In 1910, the 435 ft (133 m) Newhall Auto Tunnel was built by Los Angeles County[citation needed] a quarter-mile northwest of Beale's Cut.

[7] The pass is named after the local businessman Henry Newhall, whose land holdings formed the basis of the city of Santa Clarita.

Over time he purchased a number of properties in the state, the most significant being the 46,460-acre (188 km2) Rancho San Francisco in northern Los Angeles County.

Due to the sandstone composition of the mountain that was saturated with water and oil, frequent cave-ins occurred and the bore had to be constantly shored up by timbers during excavation.

The initial location for the north end of the tunnel was near Lyons Station Stagecoach Stop, which was abandoned due to frequent cave-ins caused by oil-soaked rock.

On September 4 Charles Crocker notified Southern Pacific that the track had been completed on the route between San Francisco and Los Angeles.