Description The Hike To Koosah Falls, ORKoosah Falls, also known as Middle Falls, is second of the three major waterfalls of the McKenzie River, in the heart of the Willamette National Forest, in Linn County, in the U.S. state of Oregon. The waterfall is notable for its main drop of 64 feet that plunges into a considerable pool, south of Santiam Pass. Wikipedia