Flowing down from the Wind River Mountains, the Middle Fork of the Popo Agie River drops into Sinks Canyon, disappearing underground for nearly a quarter mile. Carved out during the age of glaciers, the porous Madison limestone creates an unusual underground passageway for this fast moving river. Mysteries surround the disappearing act, causing geologist to speculate on what happens underground. The water flow, taking two hours to move just a quarter mile, is quite puzzling, as well as its rise in temperature.
   Sinks Canyon State Park and neighboring Popo Agie Wilderness are encompassed by the Shoshone National Forest. Here in Wyoming, near Lander, park guests find there’s a lot more to the area than a disappearing river. Contrasting forestland and a dry sagebrush and juniper landscape are home to a variety of wildlife and plant species. While bighorn sheep and mule deer are easily spotted, park visitors may also see marmots, moose, beavers, and black bear. Birders will be excited to see green-tailed towhees, golden eagles, and kestrels. The western tanager, mountain chickadee, blue grouse, and Townsend's solitaire may be much harder to find in the thick conifer forest.
   Downstream, the Popo Agie emerges into pool, called The Rise. Rainbow trout hang near the edges of the pool, eager for a handout. Upstream, the Popo drops in a series of cascades, with the largest waterfall about 60 feet. During the early summer, when the river is swollen with snowmelt, the Popo Agie Falls are simply spectacular.

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