The question had both "West Coast" but also "California" in particular. I PMed OP to ask whether they cared about Alaska, and they said I could post this.

There's the FAQ page on North America, specifically 'How come America was not "discovered" via the Bering Strait?' by /u/Reedstilt (including multiple waves of Indians). For when any part of the Far East became Russian, you might look for the mention of Dezhnev. For native contact, I also found "Russia is so close to Alaska, why didn't the Russians discover North America well before Columbus?" by, appropriately enough, /u/The_Alaskan (but ignore the descendant replies).