By Jared Ebersole in Video — 29 Mar 2026

Why Boston Kept One Ugly Beam From the Big Dig

The Dewey Square Pylon is a small leftover from one of America's most expensive and consequential highway projects.

The ugly beam is doing something most monuments are too polite to do.

It is reminding Boston what used to be there.

Where it is

Dewey Square Pylon and Bent 38, near 99 High Street, Boston, MA 02110.

Before the Rose Kennedy Greenway, before the skyline opened back up, before downtown Boston could breathe across its old waterfront, there was the Central Artery: an elevated highway cutting through the city. It was built for a mid-century idea of progress, when the answer to traffic was often to drive a road straight through the neighborhood in its way.

At first, the road looked useful. The Central Artery opened in the 1950s for roughly 75,000 vehicles a day. By the 1990s, it was carrying close to 200,000. The Federal Highway Administration notes that its accident rate was four times the national average. The Congress for the New Urbanism describes the old corridor as congested for much of the day, with the elevated structure separating downtown from the waterfront.

Boston could have rebuilt the scar.

Instead, it buried it.

The Central Artery/Tunnel Project, better known as the Big Dig, rerouted I-93 into tunnels, extended I-90 to Logan Airport through the Ted Williams Tunnel, built the Zakim Bridge, and removed the old elevated highway from downtown. In its place came a series of parks and public spaces where the highway had once stood overhead.

That is the simple before-and-after version.

The construction version was much harder. You cannot casually demolish a highway that hundreds of thousands of people use. For large stretches, engineers had to build the new underground highway while the old elevated one kept carrying traffic above. The supports for the old roadway were often exactly where the new tunnel wanted to be.

So crews used a temporary logic that feels almost impossible from the sidewalk. Slurry walls were built deep into the ground to form the future tunnel walls and stabilize the excavation. Temporary bracing carried loads. Portions of the old highway support system could be cut away as the deck was transferred to new support conditions. The city kept moving while the ground under it was being rearranged.

That is why the Dewey Square Pylon matters. It is not beautiful in the conventional sense. It is a remnant of the old elevated Central Artery, left standing near the place where the highway once dominated the street. It marks the scale of what disappeared. Without it, the Greenway can feel inevitable, as if downtown Boston was always supposed to have this open strip of sky.

It was not inevitable.

It cost decades, disruption, engineering risk, political fights, and an enormous amount of money. The official project cost is often listed around $14.6 billion, while later accounting including interest has pushed the true cost well above $20 billion. The Big Dig became a shorthand for cost overruns and megaproject pain.

It also worked in important ways. Travel-time measures improved dramatically after the main work was complete, including a reported 62 percent reduction in vehicle-hours of travel across the Central Artery, airport tunnels, and related Storrow Drive connection. The elevated highway came down. Downtown reconnected to the waterfront. Land once trapped under ramps became civic space.

Then tragedy became part of the story too.

On July 10, 2006, a section of ceiling in the I-90 connector tunnel collapsed. Concrete panels and hardware weighing about 26 tons fell onto a car, killing passenger Milena Del Valle and injuring driver Angel Del Valle. The National Transportation Safety Board traced the failure to epoxy anchors that were not appropriate for long-term sustained overhead loads. The problem was not that Boston tried to bury a highway. The problem was a specific failure in a suspended ceiling system, made worse by warnings, workmanship, oversight, and material choices.

That distinction matters because the Big Dig is both a success story and a cautionary tale.

It shows that a city can undo a destructive highway. It also shows that undoing one is not clean, cheap, or automatically safe. The same project that gave Boston the Greenway also gave infrastructure textbooks one of the clearest examples of how small components, poorly specified or poorly monitored, can become fatal inside a megaproject.

The beam at Dewey Square sits between those meanings.

It is ugly because the thing it remembers was ugly.

It is worth keeping because the city should not forget how much work it took to remove it.