 Starting approximately 40 million years ago in the middle Eocene , a braided river system called the " Ancestral Rogue River " flowed through the region where the Rogue Valley is now carved . For about 2 @.@ 1 million years , the river deposited what is now known as the Payne Cliffs Formation by laying down a thin conglomerate , followed by <unk> sandstone and siltstone . Between 10 and 20 million years ago , the uplift that created the nearby Klamath Mountains caused an incision that formed the Rogue River valley . Vertical erosion , or downcutting of the Rogue River continues to keep pace with the recent uplift , with about 690 feet ( 210 m ) of erosion occurring in the past seven million years . 
