Nicholas R. Cataldo wrote an interesting column for the San Bernardino Sun about the old trails that winded through the Cajon Pass area north of what is now the Los Angeles metropolitan area. In fact, there was a toll road along Cajon Pass as early as 1861. It later became the National Old Trails Road, which later became Route 66, which later became Interstate 15.
Go read it. It’s a fascinating read about how roads evolved..