In all our years of travel & living in the west, we've encountered exactly 2. One was in an old abandoned park in southern Washington along the Columbia river. We pulled in, turned the kids loose & told them to watch for rattlers. We made lunch on the tailgate, then called them in. Not five minutes went by, and a rattler heads our way from the area the kids were playing in. I grabbed a stick, and trying to get it to coil/strike - no deal - it just wanted to go. We let it go on its way, but it was a good introduction to rattlers for the kids.
The second one was a small rattler in an RV park in South Dakota:
They don't "coil", they form a bit of a spring. This one was about a foot long, and it's strikes were all of a couple-three inches. This one didn't initially rattle, but when it did, it was all but impossible to hear.
It was just at nightfall; we were walking back from the laundry/pool hall. My brother & sis-inlaw were ahead of us by a couple minutes. I was looking forward & up at the evening sky when my wife commented that she thought there was a snake in front of me. Whoa! I played with it with a stick while she headed on to the RV to get the relatives and my camera.
It was an educational exercise! We had been watching for them all across the area, and had been in some areas where they live, while geocaching. Always be wary...