It states that all straight bourbon is a sour mash, however the Woodinville Whiskey Company will be putting out a straight bourbon in a few years and it will not be a sour mash and probably some of the other micro distillers may be in this boat also. There are also some more like # 13 with the Four Roses not being distributed in the US
I just have way too much time to F around lately
11. What is the difference between straight bourbon, blended bourbon and sourmash bourbon?
Today, all straight bourbons are produced by the sour-mash method. In the sour-mash method, backset (liquid from a previous distillation) is added to the mash in addition to yeast. The backset helps to make the next batch of bourbon similar to the previous ones by passing on some of the characteristics of the previous batches (this is similar to using a "starter" when making sourdough bread). Straight bourbons are produced in accordance to the laws mentioned in FAQ #1 What is bourbon? and contain only undiluted grain distillates. Blended bourbons contain at least 51 percent straight bourbon mixed with neutral grain spirits.