The four mile stretch of Highway 101 that connects the Conejo Valley with Pleasant Valley is the Conejo Grade. Originally constructed in 1915 with no less than 49 twists and turns, the Conejo Grade has been straightened and widened over the years to accommodate growing population needs.
The shot above was taken in 1957 by aerial photographer Walt Dibblee. You can clearly see remnants of prior iterations of the Conejo Grade from above. You also may notice the lack of, well, much of anything, at the top of the grade in Newbury Park.
Below is another shot, a bit closer up. As you can see, the Grade was not quite as wide in those days.
Thanks to Walt's son Steve Dibblee of VenturaViews.com.