Springdale is a remote natural wave on the Yellowstone River near the small Montana town of the same name, with access off the Springdale Bridge. It only turns on at high flows, generally during spring runoff, and goes quiet the rest of the year. There isn't much documented about this one beyond that — it's an out-of-the-way spot that hasn't built up much of a track record among river surfers. If you're passing through during peak snowmelt it's worth a scout, but don't plan a trip around it without local intel.