Last year the Tour of California, for the first time, rode the east side of Patterson Pass, the last climb in the stage into Livermore. The result was domination of the Strava leader board as the group blasted over the climb, down the other side, into the city for a few finishing circuits, then to the sprint which was dominated by Peter Sagan.
The Strava segment:
Here's my rendering of the profile data:
It begins gradually, traversing up the windmill-capped hill until the "oh-my-God" climb which leads to the pass. Although the view of this section is dramatic, the profile shows the grade is only 12%, which can cause distress but is not in the league of the steepest climbs in the Bay Area. Using my climb rating index, it rates 74% as high as Old La Honda Road.
I've ridden this climb in two major events: the Devil Mountain Double and the Patterson Pass Road Race. In the former, it comes between Mount Diablo and climbing the west side of Mount Hamilton. It's a noteworthy challenge, but in comparison to these other climbs, and Sierra Road which follows, it's a small obstacle to be traversed doing as little damage as is practical.
In the road race, it's another matter. One time I rode the climb in the E3 race strongly at the front before I was squeezed off the right side of the road, crashed, and the watch on my wrist tore open the skin there, leaving a substantial scar. Another time the headwinds were so strong over the pass that even the hefty sprinter types could crest with the lead group: the climb was completely neutralized since those at the front were riding into a block headwind which, even with the 12% slopes, prevented anyone from getting off the front.
So this climb has a lot of history. It's been used in many cycling events over the years, from training rides to recreational rides to amateur races to the Tour of California. Just don't panic when you see the final run to the pass.