SEARSMONT, Maine — Falling autumn leaves and an agitated garter snake provided the most action Saturday morning on a walk along the Georges River Canal, but 150 years ago, the scene would have been very different.

The canal was one of the first to be built in the United States, according to the Georges River Land Trust, which built and maintained the trail system there. The first canal section, which stretched from Appleton to Warren, was completed in 1793 — but a more ambitious effort was begun 50 years later by a consortium of businessmen. They wanted to move goods like lumber and hay on the water, but needed a way to navigate around the swiftly flowing Georges River, volunteer Dave Getchell Sr. of Appleton said on a guided walk of a section of the canal.

So they dammed portions of the river and created a series of canals and locks next to it that allowed men to pole shallow barges loaded with goods up and down the river.

“They could barge goods from Searsmont to Warren,” he said — a distance of about 40 miles.

The earth-and-wood canal system was used for about 10 years before washouts and changing times caused it to be discontinued, Getchell said.

But the quiet path on the Robbins Section of the Georges River Canal shows where the canal was and how it worked.

“The thing about the canal is to see something close to 150 years old and uncover all the interesting developments,” he said.

One of those developments is the “mystery dam.” That’s what Getchell has dubbed the dam that he and others knew must have existed but of which they could find no sign. The canal follows a straight line west of the river for half a mile, then stops 10 or 12 feet above the river. The history buffs knew that’s where the dam must have been located — and figured it was about 25 feet high — but there is no remaining sign of it.

“It’s just disappeared entirely,” Getchell said.

He pointed out a spot where a wooden lock had been washed out by fast-moving water. The locks were used to lift and lower boats and barges around the dams.

One visitor, Alan Plutchok of Vallejo, Calif., said he thought the canal walk was fascinating.

“The exciting thing is to think about how an area that seems so relatively quiet had so much activity 150 years ago,” he said. “You look at it, and you see the labor involved. There’s a lot of shovelfuls of dirt that were moved.”