Father Juan Crespí camped near what is now Castaic Junction in 1769, at which time there was a "thriving Indian village" on the site.[2]
Castaic Junction was the official southern end of the Ridge Route. The name dates to 1887, before highways were built, when a railroad siding was set up at the junction.[3]
A highway bridge at Castaic Junction was destroyed by the collapse of the St. Francis Dam in 1928.[4]
Just beyond the north end of the Magic Mountain parking lot is the site of the adobe ranch house for the historic Rancho San Francisco, a Mexican land grant that encompassed the Santa Clarita Valley from Piru to Canyon Country.[6]
According to local legend, icon James Dean ate his last meal at the Tip's Restaurant formerly at the crossroads of Highway 126 and The Old Road before he drove on north.[7][8]