Toward the end of our fifth day on the river, not quite 90 miles north of where we had cast off from Pier 40 in Manhattan and still a good 70 miles south of our goal -- Waterford, New York, where the Erie Canal begins -- we rounded Esopus Meadows Point. In different conditions we might have stopped to admire the picturesque island lighthouse and ponder the green majesty of the Catskills rising behind. But with a stiff northwest breeze blowing and the tide beginning to ebb, it wasn't anywhere a small, human-powered, northbound vessel wanted to be. Taking a turn in the coxswain's seat while my three crewmates rowed, I steered left in hopes of finding a wind shadow along the shore, and maybe a little less current.

This was a different Hudson than we'd seen so far. The ever-present railroad tracks had peeled back from the river's west bank a few miles earlier, and gone too were the stately mansions of Hyde Park, with their white columns. Here there were dented tin skiffs pulled up in the reeds, and plywood fishing shacks, and run-down Victorians whose lawns sprouted rusting Maytags and Fords. Up in the bow Randy shipped his oar and took out his camera. "This reminds me of the place where my girlfriend's dad lives," he said. "Pennsyltucky."

Maria, in the stroke seat, and Mary, in the three seat, rowed on, and slowly we worked our way up under the lee of a little promontory. There was a turnout on the road, and there were about a dozen fishermen standing on the bank, Billy Bobs in truckers hats, a few Vietnam-vet types in duck jackets, and, incongruously, two Rastafarians in towering knit caps. Who knows what they made of us: two 40-something slackers, two teenage girls, and Marshall, Randy's wolflike mutt, all packed into a slender white-hulled rowing gig with four pink-spooned oars.

Actually, we found out. When Randy hazarded a friendly wave, one of the Rastas waved back, middle finger extended. Randy laughed and kept waving, slowly pulling in his own digits until he was returning the salute. It was absurd: the girls straining to move the boat upriver, me steering a fine course between the current and the fishing lines, and Randy and the Rastaman grinning like idiots as they flipped each other off.

When we got around the point I pulled out the chart. The Port of Kingston's Rondout Creek, that night's destination, was still two miles away, upwind and uptide. "It looks like we're gonna have to crank on it for a while here," I told Mary and Maria. "Let me know when you want to switch out."

"No way," said Maria. "I'm rowing." She cleared her throat and spat manfully over the starboard gunwale.

When people heard about our trip upstream, their first question was usually why we weren't going the other way, "with the current." But that's the whole wonder and magic of the Hudson, and the thing that made it the engine of commerce and industry that it became: America's first superhighway. Technically speaking the lower Hudson is what geologists call a drowned valley, a fjordlike tidal estuary. While the salt-fresh line typically hovers 60 to 90 miles north of Manhattan, the tides themselves slosh back and forth all the way to the confluence with the Mohawk River at Troy. Thus Henry Hudson's feat, in 1609, of getting the then state-of-the-art Half Moon all the way to what's now Albany in just 11 days -- and our plan to outdo him by a day or two.

Our own Half Moon was called the John Magnus, after a plucky 14-year-old coxswain who'd steered a similar 26-foot Whitehall gig, the water taxi of its day, to victory in an 1824 match race against the British that drew a crowd of 50,000 people to the banks of the harbor. It was a loaner from a New York City community rowing program called Floating the Apple, which builds mahogany plywood-epoxy Whitehall replicas in order to further its mission of "restoring public access, particularly for young people, to our urban waterways." The organization's founder, Mike Davis, liked the idea of an emissary vessel spreading his message upstate.

Getting the crew together was a bit more complicated. Photographer Randy Harris, a winter camping buddy, volunteered immediately, but another friend who'd said yes bailed at the last minute. Then, miraculously, a pair of 19-year-old stalwarts stepped forward. Mary Betts, a college junior, had done a lot of rowing with Floating the Apple. Later in the summer she and Maria Kearney, a boat-building student from Washington, were headed to Genoa, Italy, to compete in a traditional-boat regatta called the Atlantic Challenge. Convinced the Hudson trip would be ideal training, they packed a capacious tent and announced their willingness to share it -- with Marshall the dog.

One obstacle remained: where to camp? Personally, I'm a believer in what the Norwegians call allemannsretten, or all people's right, a legally enshrined principle that allows wayfarers to pitch tents anywhere they like, even on private property. I suspect that I may be in the minority on that here in the U.S., but thankfully there are other, more diplomatic types pushing in the same direction. About 14 years ago a group of New York kayakers and other small-boat enthusiasts banded together to create something called the Hudson River Water Trail, a series of boat launches, campsites, bathrooms, and information kiosks that would, they hoped, ultimately run the length of the navigable Hudson. The governor strapped on a personal flotation device and came out for a photo op, and a few sites were actually designated. But there are still some big gaps in the system.

We discovered as much on day one, when a horrific rainstorm left us well short of the first Water Trail campsite, at Croton Point Park, a very ambitious 37 miles upriver. Wet and dog-tired, we made it just half that distance, putting in at a park in Alpine, New Jersey, opposite Yonkers. There was an elevated veranda with a vaulted roof, perfect for hanging our gear, and no one around but a few mellow fishermen. So we clomped upstairs and camped right there on the wooden floor. It was a surreal night, with the sodium glow of Yonkers shimmering across the water, the thunder of passing trains, and the not-so-gentle roar of a generator on a barge anchored midstream. Even on the wildest stretches of the Hudson, we learned, the throb of the almighty diesel is never far away. And then at dawn, a new sound: the rhythmic whopping of helicopters -- not military ones, but sleek machines ferrying big shots downriver to the towers of Gotham.

North of Kingston the Hudson grew wilder. Shaggy willow and ash trees overhung the banks and around every point another blue heron would flare out from our bow. At Saugerties we ducked into Esopus Creek to wait out the tide, then walked up the hill to find lunch. A kid in a pizza parlor took our order, then listened wide-eyed as Randy told him what we were up to. "Oh, man," he said, gazing distractedly around the fluorescent confines of the shop. "I'd like to do that."

That night we found the best campsite of the trip, a driftwood-filled clearing on an unnamed dredge-spoil island in Inbocht Bay, at mile 109. The next morning we spied a Department of Environmental Conservation sign nailed to a tree: CRITICAL HABITAT, NO ENTRY FROM JAN. 1 TO SEPT. 31. I can't say I felt too bad about it. Or, looking back, about the other publicly owned islands on which we had supposedly trespassed: Round Island, in Bear Mountain State Park, whose Revolutionary WarŠera fortifications offer perfect views up and down the river, or Pollepel Island, which is normally off-limits to the public due to a massive fire that burned down its landmark faux Scottish castle, built by eccentric arms dealer Francis Bannerman.

It's always fun to break the rules. But for me, sneaking onto forbidden islands and commando camping are ultimately political acts. In theory, you and I own the water and the foreshore that runs along it; in practice, as old industrial properties are steadily converted to private waterfront enclaves (farther south we'd seen the condo-encrusted points of the Tappan Zee and Haverstraw Bay) or nature preserves, getting to them is becoming harder and harder. While I'm all for bald eagles (which are, by the way, maintaining their population), does it really make sense to create pristine, human-free wilderness zones on the Hudson, where trains and barges run all night, the islands are man-made, and, in any case, people have roamed for millennia? The way I see it, if we're really serious about restoring the river to its former health and grandeur, people are going to need to know and care about it firsthand. That means more access, not less.

We spent our last night at the Van Schaack campsite on Bronck Island, at mile 128. Thanks to more headwinds we got there at dark, and found one other person camped there, a woman with a tiny kayak and a minimal tent. She radiated eco-disapproval: of our dog, our big fire, and our grotesquely oversize boat. But her tone changed to envy when we told her about our previous night's camp spot in Inbocht Bay. "Oh, we call that Echo Island," she said. "I've stealth-camped lots, but never there."

The next morning, just a mile into our row, a good breeze from the south filled in. We put the sail up, and by midafternoon the towers and overpasses of Albany were sliding past. Just north of the capital two deputies in a sheriff's boat overtook us, then throttled back. At that point we must have looked like a cartoon from a boating safety seminar: nobody in a life jacket, beer cans rolling around the bilge, Marshall precariously perched on the gunwale. But the girls waved and smiled, Randy and I nodded gravely, and the sea cops buzzed off.

At six we reached the cavernous Federal Lock at Troy, the stepping stone to the upper Hudson. We still had two miles to go to our takeout in Waterford, but it was the end of our sea voyage. As the giant doors swung closed behind us and we were borne up on the foaming waters, the lockmaster came out of the control booth, clipboard in hand.

"Vessel name?" he called down.

"John Magnus."

"Length?"

"Twenty-six feet."

"Registration number?"

The four of us looked at one another blankly. "Uh, I don't think we have one," I said. "We're not motorized."

The guy lowered his clipboard and gave our trusty little ship a closer look. "What?" he said. "There's no motor in there?"