Back in February 1925, before there was a U.S. 101, the folks in California’s highway department were proud of the solution they’d come up with to “warn and protect motorists at the sharp curve approaching the San Mateo Creek bridge, northern San Diego County, where many deaths have occurred recently.”

It was a big, canvas sign that said “SLOW — DANGER.”

I wonder how that would work in Interstate 5, the clogged freeway a few hundred yards west of where these photos were taken in 1925.

The coast road wasn’t even designated as U.S. 101 until November 1926; traffic on this narrow blacktop strip was resulting in “many deaths.” It was known as “Slaughter Alley” in later times. I believe the location is north of the San Onofre Nuclear Power Plant on the northern edge of San Diego County. Today, if you’re headed up I-5, this old roadway is still visible, abandoned, just west of the current frontage road.

Check out the full story on in the February 1925 edition of California Highways and Public Works.

The rest of the old highway wasn’t so safe either. Check out what it looks like today — and where you can find remnants — in Joyrides Around San Diego.  


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