A hydroelectric plant along the Farmington River in Canton that was out of use for decades is now generating about a megawatt of power, and the public is invited to see it in action on Saturday.

The town and Canton Hydro LLC are offering a rare chance to tour the powerhouse and view the all-new fish ladder and eel passage from 12:30 to 3:30 p.m.

“This is a special occasion, a great opportunity to see the plant and talk with the people who put it all together,” First Selectman Robert Bessel said Thursday. “People can go inside the pumphouse, see the new turbine, and watch the new fish ladder and eel passage on the other side. For the 10- and 12-year-olds in all of us, seeing the eels and alewives slithering up will be big.”

For generations, the brick powerhouse near the dam where Bridge Street crosses the river has been an abandoned curiosity, a throwback to the era when the huge Collins Co. factory complex was the pride — and employment base — of Canton.

The Collins Co. had built a smaller plant downstream in 1914, but as its ax- and machete-manufacturing business grew, it needed to add something more powerful. In 1935, workers completed a brick building to house a more powerful turbine, creating an operation so big that workers sometimes telegraphed the gatekeeper at the Otis Reservoir — more than 30 miles away — to increase the flow of water for the factories.

To raise the flood control gates, the gatekeeper in Otis would have to harness his horse to a mechanical lever before walking it, said Cathy Taylor, town historian.

Collins ran the operation until the entire factory complex went out of business in 1966.

A 14-year-long campaign to restore the historic power plant paid off almost three years ago, when a $6.6 million reconstruction project was completed. The turbine has been operating at reduced power since then, but this spring got to its maximum production rate, cranking out enough power to run the equivalent of 700 to 800 average homes.

Bessel credits Sen. Chris Murphy, then-state Rep. Kevin Witkos and then-First Selectman Richard Barlow with spearheading the drive to bring hydro power back to town.

They worked with a committee that brought in the Connecticut Green Bank; developer Canton Hydro LLC; the state Department of Energy and Environmental Protection; Wasserkraft GmbH, an Austrian engineering firm; Torrington-based Hemlock Construction Co. and others to finance, design and construct a modern plant, arrange power distribution through Eversource, and secure extensive state and federal permitting.

“There were a lot of people involved, but without those three this wouldn’t be here,” Bessel said.

Wasserkraft designed an automated control system that allows operators in Austria to adjust water flow and power settings remotely. A feature that the new operation has is a lengthy fish ladder.

“The Denil fishway will allow fish to get past the dam for the first time in nearly 200 years. A viewing window will allow fish to be counted as they migrate past,” the town said in a statement.