I come across them on my ranch every so often... not common to see them however. The are AMAZING:
Not on my ranch but rather a hunting ranch in the Coast Range of Calif. we used to lease I was traveling up a ridge one afternoon when suddenly I mostly 'heard' but did get a glimpse of something moving through the wild oats on the hillside. It got my attention because while at first I couldn't figure out what it was it was moving at light speed. Truly... the speed was incredible.
I could see the wild oats moving as whatever it was moved up the ridge away from me arriving at a very large oak tree... which it then proceeded to climb. AT that point I could tell it was a Black Racer. When it began to scale the oak tree I think it actually sped up.... from ground level to the top of the Oak Tree in... I really think, less than 2 seconds. It was circling the trunk as it sent up and it was a blur of motion... I barely had time to notice what it was before it reached the upper limbs and took cover.
At that time... this was YEARS ago, I did not know what a Racer Snake was so I headed to the library to do some research. Racers, as you know, are not at all aggressive towards humans BUT IF THEY WERE they'd be on you before you could blink.