Long story short, we have Montana to thank for the way our wines taste. Around 12,000 years ago, something called the Cordilleran Ice Sheet moved south from Canada into what's now the USA. This dammed the Clark Fork River, which created a ridiculously large lake known as Glacial Lake Missoula. Of course, the ice didn't last - it failed every so often, and when it did, the whole lake emptied in a series of mind-blowingly large flash floods that devastated a large area of present day Washington state.
This weekend, grrrscribbler, his partner Curtis, danlmarmot, and myself are heading out to Walla Walla for their annual Spring Tasting Weekend. When those floods hit Washington, they brought an awful lot of silt and debris with them, and that's the stuff that grapes grow in today. It's widely distributed all around the wine-growing area of the state: the soils are nearly identical regardless of where you are, be it Walla Walla, Wahluke Slope, Yakima, or the Rattlesnake Hills. The soils are also fairly uniform: just a bunch of flood debris that's perched on top of a whole lotta lava - Grande Ronde basalt, to be exact.
So, even if Washington state does have the perfect climate for wine, it's the boringness of its soils combined with their uniform geographic distribution that means you'll probably never experience a truly profound wine from the state. Yes, we do good stuff up here - a Yakima Cellars Elephant Mountain syrah will put a huge grin on your face - but when it comes to terroir, we're sorely lacking.
Oh, and Oregon? You're not off the hook either. Thanks to something called the Wallula Gap, the flood waters slowed down and backed up for a bit, but eventually all of those catastrophic floods wound up depositing much the same kind of debris in the Willamette valley, so your soils aren't anything special either. However, your weather is definitely cooler and wetter, so it's no wonder your riesling and pinot noir are better than ours. :)