Howard Street Tunnel

The 1.7-mile Howard Street Tunnel that billowed smoke yesterday is not a prominent part of the Baltimore landscape, not a source of great civic pride. Yet the tunnel, mostly ignored and unseen - even unknown to many residents - is hugely important, the way rail freight basically gets from here to there along the East Coast. And it's hardly just a functional workhorse. The 106-year-old tunnel is distinctive in many ways. It's said to be the longest underground conduit of freight on the Atlantic seaboard; the first example of heavy-duty railroad electrification in the United States, possibly the world; and a model example of soft-earth construction, built at a time when steam locomotives huffed and puffed through mostly rock-blasted tunnels.

Civil defense sirens wailed and major highways into Baltimore were closed after a freight train hauling hazardous chemicals caught fire yesterday afternoon in a century-old railroad tunnel under Howard Street, shutting down much of the city's downtown. Choking black smoke spewed from both ends of the 1.7-mile Howard Street Tunnel, and fear of an explosion or toxic fumes from a cargo that included dangerous acids prompted authorities to ban pedestrians and vehicles within five blocks of its openings at Camden Yards and Mount Royal Station.

As Orioles fans walk to their ballpark seats, just below their feet flows a giant freight conveyor belt, known as the Howard Street Tunnel and all but unknown to those passing overhead on the sidewalks and asphalt.Some 30 million bricks went into this sturdy relic of railroad engineering. Excavated more than 100 years ago, the tunnel is used now by CSX Transportation, which says it is the largest subterranean conduit of rail freight along the Atlantic Coast.Most days, about 40 trains pound through this cavern, a 1.7-mile channel of Stygian darkness and dank, musty air infused with a dense humidity born of outside water seeping down the curving masonry walls.

If you opened a Baltimore newspaper 100 years ago, a big ad on page one jumped out like an express train: "BELT LINE OPEN."What was new and marveled at in 1895 is today quietly overlooked, often forgotten.But listen on a rainy or humid day. Turn your ear to the dull roar and mournful whistle of a freight train in the Howard Street Tunnel, a splendid piece of 19th-Century engineering that turns 100 today.Nearly 1.7 miles long, the tunnel has become the largest underground conduit of rail freight on the Atlantic Coast.