LeHardy Rapids is the lake's true northern end, a short stop on the right for northbound drivers, with a vault toilet. Cutthroat trout leap here in spring, and the river's rise and fall is tied to the caldera moving beneath it.
LeHardy Rapids, half a mile ahead on your right. Pull in, and you'll see where the lake really ends. You'd think it stopped back at Fishing Bridge. It doesn't. The elevation of the lake's north end doesn't drop substantially until these rapids, and that makes them the lake's northern geologic boundary. From here on, it's a river. The Yellowstone crosses the caldera's axis near here. When the caldera rises, this outlet rises and water backs up into the lake. When it sinks, the outlet drops and the lake drains. That little run of whitewater is the plug in the bathtub, and the volcano has hold of the chain. In spring, watch the water for cutthroat trout leaping upstream. There's a vault toilet at the pullout. Turn right when you leave. And since this is where the river starts, here's its name. It has nothing to do with the yellow canyon ahead of you. The park says Hidatsa people called it the Yellow Stone for the bluffs of yellow sandstone that frame it in eastern Montana, and French traders turned that into Roche Jaune.
Photo: NPS Photo / A. Falgoust · Public domain (NPS; PD-USGov-NPS)