The freight trains that labored to climb through Baltimore’s historic Howard Street Tunnel disappeared a few weeks ago. For the first time in 130-odd years, the slow, dull roar of engines climbing a steep grade through Remington, Charles Village, Harwood and Clifton Park went silent.

The hiatus is temporary.

A small army of construction workers, clad in fluorescent safety vests, and helped by earth movers and diggers, is re-digging — essentially lowering — the principal rail route through Baltimore.

CSX, the transportation company that owns the tunnel, anticipates having its enormous campaign finished by the end of this year so that its rail cars will be able to carry double-stacked containers under the streets of Baltimore and some of its neighborhoods.

The project will permit CSX to run tall, double-stack, intermodal trains on its own tracks through the Mid-Atlantic states for the first time.

During the construction period, some trains will be redirected over the Norfolk Southern’s Lurgan Branch, Harrisburg Line to Norristown, Pennsylvania and on to Philadelphia.

Almost unnoticed during the cold weather last month, crews removed the rails. The work began adjacent to M&T Bank Stadium, the southerly end of the tunnel. The rails also left the Belt Line, the open depression that parallels East and West 26th Street and snakes along the contours of the Jones Falls Valley in Remington.

A stone portal bridge that carried automobile traffic from the 2500 to the 2600 blocks of Guilford Avenue disappeared, leaving behind massive pieces of 1890s construction stones. They soon left in dump trucks.

Other bridges the railroad encountered — the massive North Avenue Bridge and the smaller Sisson Street Bridge (a popular auto shortcut through Remington) are also being reconstructed.

“The initiative aims to increase vertical clearance in the … tunnel and address 22 additional obstructions along the corridor between Baltimore and Philadelphia, improving connectivity to key Midwest markets,” says a CSX statement.

“This is a tremendous opportunity to alleviate a restriction on our network and open up new opportunities for CSX,” said Ed Sparks, CSX chief engineer of bridge design and construction. “We’re starting something big today.”

The aim is to improve what the railroad calls its I-95 corridor while better connections to the Seagirt Marine Terminal Intermodal Container Transfer Facility at the Port of Baltimore with other markets.

“It strengthens the Port of Baltimore’s competitiveness with other East Coast ports,” said Brandon Knapp, CSX senior director of Mid-Atlantic construction. “This project benefits CSX while also boosting the region’s economy.”

In a statement, Mike Cory, CSX executive vice president and chief operating officer said, “We have a lot of people on this property, not all of them CSX employees, but we’re all one team.”

There are several financial players here, including CSX, the U.S. Department of Transportation, the state of Maryland and the Commonwealth of Pennsylvania.

The tunnel and the Belt Line have a fancy historic pedigree. It was hand dug, with maybe a steam shovel, between 1890 to 1895. Listed on the National Register of Historic Places, it was designed by the prominent civil engineer Samuel Rea.

Some 2,400 laborers spent five years on hard labor. The Sun reported the builders encountered a pesky stream at Howard and Centre streets. That same stream later plagued construction of an addition to the Walters Art Museum. Then in 1997, it created an urban sinkhole that severed a gas line and gave downtown Baltimore quite an unwelcome fireworks show.

In August 1892, the tunnel construction cracked the walls of Baltimore City College (Howard and Centre) and it had to be dynamited and demolished.

“The scene in front of City College is one of havoc,” The Sun said. “Crowds of curious sightseers and former students visited the ruins during the day.” The old B&O Railroad made good and paid for the damage. That replacement structure stands and is now apartments.

The tunnel made news in 2001 when a train caught fire within the cavity and burned for hours. A car full of computer paper took days to burn itself out.

The tunnel contractor was John B. McDonald, born in Cork, Ireland, who was paid $7 million for his efforts. A fellow contractor, Lawrence McCabe, built the Belt Line from Bayview to Huntingdon Avenue.

A locomotive, helped along by newfound power in an electrical system, tested the big dig on Feb. 1, 1895. This experimental train included 22 cars filled with West Virginia granite. It passed the test, and The Sun declared “A Railroad Triumph.”

Rea’s success in Baltimore gave him a new job at the Pennsylvania Railroad. He also was memorialized in a life-size bronze statue at Pennsylvania Station in Manhattan.

McDonald, who built the Howard Street Tunnel, was also a tunnel hero. He got the task of building New York’s first subway, the Interborough Rapid Transit Co. He died in 1911 at his home in the Dakota apartments overlooking Central Park.

He did not live to see the filming of the 1969 movie “Rosemary’s Baby,” nor the arrival of John Lennon and Yoko Ono, also famous Dakota residents. McDonald was a modest man. Of his tunnel labors, he said, it was “just like building cellars.”

Have a news tip? Contact Jacques Kelly at jacques.kelly@baltsun.com and 410-332-6570.