NORTH ADAMS, Mass. (NEWS10) — The historic Hoosac Tunnel remains closed to freight trains after a partial collapse last week.

As Pan Am Railways continues assessment and repairs, NEWS10 ABC took a look into the tunnel’s storied past.

At the North Adams Museum of History and Science, there’s a replica of the 150-year-old Hoosac Tunnel. It’s considered a remarkable feat of engineering.

“The claim to fame in North Adams is the Hoosac Tunnel,” said historian Chuck Cahoon.

He says the tunnel stands as a testament to 1800s ingenuity.

“No one had ever built a tunnel that long before,” he said. “They did not have the equipment to do it when they started. It was all invented on the project.”

Methods that are used in tunnel digging even today. The 4.75 mile tunnel provided a route to Boston turning North Adams into booming mill city.

“It actually allowed North Adams to be built into the city that it was,” said Cahoon.

Digging began in 1851 and took 22 years with 200 lives lost along the way.

“They were using high explosives, so there were many accidents,” Cahoon said.

Cahoon says the issues workers faced back then contributed to last week’s collapse — a portion of loose soil near the west entrance.

“They had to line the opening with brick pipe to hold the loose rock back, and over the years, water has percolated through and every once in a while some collapses,” he said.

He says it’s happened three times before, but the latest is the worst and could result in a major repair known as “daylighting.”

“In which they would cut off all the roof of the tunnel back maybe 300 to 1,000 feet.”

Shortening the tunnel, and possibly removing the granite facade, seen everywhere from the town seal to Cahoon’s belt buckle.

“We don’t really want to lose it, and we wonder if it’s going to happen when this process gets done,” he said.

However it’s done, Cahoon is confident a repair will keep freight on the move for centuries to come.

Historic photos courtesy of Jerry Kelley, whose website can be found by clicking here.