Where I live, there are over two dozen species and sub-species, including two venomous (which are the main ones I study in the field). My friend and I have been hiking and driving through the mountains for over three years now seeking and recording our encounters for a short documentary. Snakes are very misunderstood, and they're a much needed natural predator. The environment and our health depends on it.
If your travels ever end up way out here, I'd be happy to introduce you to a living, thriving rattlesnake den in the mountains. It's amazing to see so many different species and sub-species of snakes living together.