In the Willamette Valley, there are mysterious stands of aspen far separated from any other wild aspens, whose origin is completely unknown. We believe these trees were brought here by cataclysmic floods originating in Montana ≈15,000 years ago. Through in-depth genetic comparison of these “lost aspens" with others throughout the west, we can determine their origin. This could be the first study showing dispersal of any species by massive floods.