WASHTUCNA-The Palouse River runs through a narrow cataract and drops 200 feet to a churning bowl. From there, the current moves swiftly, through a winding gorge of columnar basalt, to its southern end at the mighty Snake River.

Carved more than 13,000 years ago, Palouse Falls is among the last active waterfalls on the Ice Age floods path. This natural wonder was named Washington's state waterfall in 2014, when the state Legislature passed a bill written by third, fourth and fifth graders of the nearby Washtucna School, who advocated for the designation.

Palouse Falls State Park's lush 105 acre...