Sinks Canyon State Park in Wyoming’s Wind River Range is known for a remarkable section of the Middle Fork of the Popo Agie River, which vanishes into the limestone Sinks and reappears downstream at the Rise by an unknown underground route. Shaped by glacial action in the Madison Limestone, the canyon also preserves evidence of human use reaching back to the last ice age. In the late 19th and early 20th centuries, it supported a sawmill, ski area, and hydroelectric plant. Protected through land acquisitions and donations, the park was created in 1970 and is valued today for its unusual hydrology, diverse ecology, wildlife, and recreation.