In the fall, when many rivers are reduced to a trickle, the Kennebec is still churning Class IV whitewater through a steep-walled granite gorge in remote western Maine. This makes for what’s arguably the wildest and most consistent river trip in the Northeast, with no signs of civilization anywhere on the 12-mile run. True, the Kennebec owes its late-season flow to releases from the Harris Station dam, but there’s a big upside. Several times a year—including this September 8 and 22—the dam’s operators double the flow to 8,000 cubic feet per second. “We suddenly get big, curling-back standing waves 10 to 12 feet high,” says Northern Outdoors president Russell Walters. “You just don’t see that kind of thing in inland rivers in the middle of September.” The one-day trip is a roller-coaster anytime you run it—look out for the Three Sisters and Maytag rapids—though it mellows out after the upper gorge, where you can swim or paddle inflatable duckies down the Class II sections. In addition to day trips ($79), Northern Outdoors runs a lodge, cabins, and a brewery below the takeout on the Lower Kennebec (doubles at the Forks Resort Center, $105).