EDITOR’S NOTE: This is the last in a series of articles following the 1993 Penobscot Riverkeepers Expedition from Quebec to the sea.

CASTINE — They talked, a month ago, about following the path of a raindrop from its highest point of impact, down the length of the Penobscot River to the sea.

The three men and a woman who call themselves the Penobscot Riverkeepers hiked that day on a mountain straddling the Maine-Quebec border. They followed moose tracks under a hot, cloudless sky, until they found a tiny spring that would lead them to the river.

On Sunday, 29 days and 240 miles away, they finished their journey. Paddling their canoes among fluorescent lobster buoys, they looked out to a horizon of misty islands and slate-colored sea. They were joined by five canoes and a kayak; at the Backshore in Castine, more than 60 people waited to greet them.

As the Riverkeepers landed, townspeople put wreaths of lilacs on the canoes. The rain began to pour.

The warmth, if not the dampness, of the reception echoed meetings with people up river: the couple who welcomed them with apple pie at Pittston Farm, 116 Millinocket sixth-graders who cheered on the causeway at North Twin Dam, the slide show under the stars at Mattawamkeag.

Those were the rewards of an expedition intended to remind a state of the river in its back yards. People, they found, are turning toward the Penobscot with new interest.

Not all the greetings were so kind. Workers at Ripogenus Dam had only stares for the canoeists as they portaged. At the Great Works dam in Old Town, there was no portage trail at all. Paddlers had to hoist a canoe over a barbed wire fence, then climb it themselves before they could continue down river.

Expedition members watched, too, as the river itself received uneven treatment.

On the south and west branches, the state maintained meticulous campsites along pristine shores. On the main stem, just miles from Bangor, the Penobscot Nation kept its islands as unexpected pockets of wilderness. Fishermen along the way reeled in fighting bass, where just three decades ago, the water was so foul it would eat through leather.

The Riverkeepers also saw the Penobscot manhandled. Repeatedly, it was dammed, flooded, diverted. In places, it disappeared entirely into mill buildings; elsewhere, it vanished into underground tubes. When it reappeared, it sometimes did so quietly. In other spots, it boiled up the color of root beer, with a chemical stench.

So it was yet another surprise for the Riverkeepers to see how clean the water looked here, where the river feeds the Gulf of Maine. Canoe paddles were fully visible, deep into each stroke.

Expedition co-founder Jeff Hunt said that he had not seen the water look so clear since North Twin Lake. That, too, was the last place the group had heard so many loons chattering. And here, the dark, rounded fin of a harbor porpoise rose above the water from time to time.

Roger Merchant, who hatched the idea of the expedition with Hunt last summer, saw a less obvious sign of life here. The cycle of the tides, he said, reminded him — on a grand scale — of the rhythmic surge of water out of that first spring on Sandy Bay Mountain.

Together, on a rocky beach just around the point from the Backshore, expedition members gathered their gear and prepared for the last, short leg of their long journey. They talked about returning to homes and jobs, and what they would take with them.

For Gary Wagner, the third Riverkeeper to paddle the length of the Penobscot, the prize was a sense of the river as a whole, not just the pieces he had been used to seeing.

“I’ll never forget,” he said, “what it was like to see it go from that little cord of water, pulsing out of the ground, to this.”

He punctuated his remark with a nod toward the vast, gray bay, where small waves were beginning to dance with the impact of raindrops.