While the St. John and the Allagash might be the wildest rivers in the area, they are not the most exhilarating. That honor goes to the Lower West Branch of the Penobscot River, a bruising 14-mile white-water flume between Baxter and Moosehead that takes in multiple Class IV and Class V rapids from the put-in at Ripogenus Dam. (Class V is defined as “extremely difficult, with large vertical drops, strong hydraulics, very swift, irregular currents in heavily obstructed channels.” Still game?)

The fun starts right away with a Class V at Ripogenus Gorge, then churns through other spills with names like Troublemaker and Exterminator Staircase before coming out at a long lake with beautiful views of Mount Katahdin to the east and finishing with a bang at a Class IV called Big Pockwockamus. Needless to say, the stretch can only be attempted by rafters and experienced canoeists in white-water craft. The Upper West Branch, by contrast, is a much more relaxing paddle between two large lakes in a region teeming with moose.

On the other side of Baxter State Park, the East Branch of the Penobscot River is a fast-running and precipitous river with many falls, short portages, and rapids, though none higher then Class III. The full trip from Telos Lake is 72 miles long and should take five to seven days. A shorter trip with excellent views of Traveler Mountain and several spectacular waterfalls starts at Grand Lake Matagamom and ends at Whetstone Falls, a distance of some 26 miles over three to four days.

Flowing southwest out of Moosehead Lake, the Kennebec River is popular with white-water rafters for its combination of gnarly rapids (rising up to Class V with the churning Magic Falls) and a long stretch of quiet water good for spotting wildlife as the adrenaline subsides. Farther south, don’t let the name of the Dead River deter you. The 16-mile rafting run is touted as the “longest continuous stretch of white water in the east” and is great fun for its nonstop action. The course takes in Class IV rapids at Humpty Dumpty and Elephant Rock, before ending with a bang at the Class V Big Poplar Falls.

River Guides

Many local guides offer trips on all of the above rivers. Close friends and 20-year canoeing partners David Butler and Tim Emery guide groups on the Upper West and East Branches of the Penobscot through their outfit Maine Path & Paddle Guides (877/632-2663, www.canoemaine.com). They also specialize in trips for families with very young children and seniors. Allagash Canoe Trips (207/237-3077, www.allagashcanoetrips.com) offers similar trips on the Penobscot along with daylong white-water trips to the Kennebec and Dead Rivers when the water is running slowly enough to make them canoeable.

One-stop shopping for white-water rafting is Raft Maine (207/723-8633, www.raftmaine.com), an association of 14 professional outfitters who have banded together to offer day trips to the Kennebec ($80–120 pp), Penobscot ($90–130) and Dead ($90–140) Rivers. The association also offers packages including lodging or camping and other wilderness activities.