It was “State Route 17” from Santa Cruz, through Oakland, Berkeley and Richmond, all the way over the Richmond/SanRafael Bridge to San Rafael. The part through Berkely was simultaneously I-80. ETA: Thus, Route 17 met U.S. 101 in two places: in Oakland, and again in San Rafael.
That stretch from Berkeley to San Rafael is part of I-580 now. Here’s an interesting anomaly: If you drive through Berkeley on that stretch of road, you are simultaneously going east and west. In one direction (actually, you are going more-or-less north) is simultaneously I-80-east and I-580-west, and conversely going the other way.