Ripogenus Gorge in Maine is a rock-walled canyon where the West Branch Penobscot River cuts across the Caribou Lake anticline. Important both geologically and industrially, it exposes bedrock that helped define the Silurian Ripogenus Formation and once carried logs from the North Maine Woods to downstream sawmills. Rivermen altered the channel to ease dangerous jams before hydroelectric development transformed the site. Construction of Ripogenus Dam in 1915 and its completion in 1916 created a vast reservoir and diverted water past the former falls to generate power for the paper mill at Millinocket. The gorge later became known for challenging whitewater rafting and kayaking.