I can't see the tip of the tail in your photo, but it looks like a Western Rattlesnake. Rattlesnakes can get aggressive if "cornered" (just like people) I'm not a Herp but timt on Mountain Project is, and may be nice enough to answer any questions you may have.
Excellent picture. The snake is the midget-faded rattlesnake (Crotalus concolor for us herp dorks). They are quite "spunky" and will not hesitate to stand their ground. You did the smart thing by getting out of his way rather than try to move him. This species has a very potent venom!
This was the most photogenic of the 30 or 40 rattlers we saw on our trip out there. Why are all rattlesnakes in foul moods? This guy was about 2 ft long and actually chased me away from the base of this climb, I didn't think they were territorial but this guy was really pissed off that day. A smaller version crawled under my tarp and scared the crap out of me when he came cruising out from under. A great place for herpetologists.