Bicycle touring on the West Coast of USA

The Pacific Coast Bike Route

I’m not sure when the first official bike route was created for the Pacific Coast, but it was well known when I first rode it in 1977.

Adventure Cycling Association “Pacific Coast” breaks the Vancouver BC to Imperial Beach in San Diego down into five maps.
Vicky Spring and Tom Kirkendall co-authored Bicycling the Pacific Coast: A Complete Guide, Canada to Mexico. There are several editions out, I would recommend checking