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Boston History

The Big Dig: The Megaproject That Tore Boston Apart—and Put It Back Together

The Central Artery/Tunnel Project took years of planning and more than a decade of construction beneath a working city. Here is how it was engineered, why it cost so much, and what went wrong.

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The Big Dig: The Megaproject That Tore Boston Apart—and Put It Back Together

For roughly fifteen years, downtown Boston lived with one of the most complicated construction sites in the world beneath its feet. The Central Artery/Tunnel Project, universally known as the Big Dig, replaced an elevated highway through the heart of the city with tunnels, built a new harbor crossing to Logan Airport and added a landmark bridge over the Charles River. It did all this while the old highway stayed open, subway lines kept running and thousands of people went to work above the excavation every day. The engineering was extraordinary; so were the costs and the controversies.

The Problem: An Elevated Wall Through Downtown

The original Central Artery was built in the 1950s as an elevated expressway carrying Interstate 93 through downtown. It cut off the North End and the waterfront from the rest of the city and cast a long shadow over the streets beneath it. It was also badly overloaded. Designed for far less traffic than it eventually carried, it became notorious for congestion and accidents.

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By the 1970s and 1980s, state transportation planners, led by figures such as Frederick Salvucci, were developing a plan to put the artery underground and build a third harbor tunnel. Securing federal funding required years of political effort in Washington, and the project’s approval in the late 1980s set the stage for construction.

What the Project Built

The Big Dig was really several megaprojects combined:

  • An underground Interstate 93. The elevated artery was replaced by a tunnel beneath downtown, later named for former House Speaker Thomas P. “Tip” O’Neill Jr.
  • A new harbor tunnel. A tunnel under Boston Harbor extended the Massachusetts Turnpike (Interstate 90) to East Boston and Logan Airport. It opened to traffic in the mid-1990s.
  • The Zakim Bridge. The Leonard P. Zakim Bunker Hill Memorial Bridge, a striking cable-stayed bridge over the Charles River, opened in 2003 and quickly became a symbol of the city.
  • Interchanges and ramps. A complex network connected the new roads to existing highways and city streets.

Major construction began in the early 1990s. The northbound lanes of the new I-93 tunnel opened in 2003, the southbound lanes later that year, and the elevated artery was demolished afterward. The project was considered substantially complete in the mid-2000s.

Engineering Under a Living City

Many of the Big Dig’s challenges came from building beneath a dense, historic downtown on soils that included old fill, clay and glacial deposits.

  1. Slurry walls. To build the downtown tunnel, crews dug deep, narrow trenches filled with a bentonite slurry that held the soil in place. Concrete and steel were then placed in the trench to form underground walls before the main excavation began between them.
  2. Keeping the old highway standing. The new tunnel was built directly beneath the elevated artery, which stayed in service during construction. Engineers had to support the old structure with new foundations while digging underneath it.
  3. Immersed tube tunnels. The harbor tunnel was built from large steel tube sections fabricated elsewhere, floated into position, sunk into a trench dredged in the harbor floor and joined together underwater.
  4. Tunnel jacking. Near South Station, the turnpike extension had to pass beneath active railroad tracks. Engineers froze the surrounding ground to stabilize it and then pushed massive concrete tunnel boxes into place with hydraulic jacks, an approach notable for its scale.
  5. Utilities and history. Crews relocated miles of utility lines, worked around subway tunnels and catalogued archaeological finds from Boston’s colonial past.

Excavated material had to go somewhere, too. Much of it was used to cap and reshape Spectacle Island in Boston Harbor, which was later opened as a public park.

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The Cost Debate

The Big Dig became a national byword for cost overruns. Early estimates in the 1980s put the project at a few billion dollars. By completion, the commonly cited construction figure was in the range of roughly $14 to $15 billion, and estimates that include long-term borrowing costs run considerably higher.

Why did costs grow so much? Analysts and auditors have pointed to several factors:

  • Scope expanded over time, including extensive mitigation measures demanded by neighborhoods, businesses and regulators.
  • Early estimates did not fully reflect inflation over a long construction period.
  • Unexpected site conditions and design changes added work.
  • Oversight of the private management consultants who helped run the project was criticized as weak.

Supporters argue that some overruns were the price of building without shutting down a major city, and that the project delivered lasting benefits. Critics argue that management failures added billions in avoidable costs. Both views remain part of the project’s legacy.

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Leaks and a Fatal Failure

The project’s reputation was further damaged by quality problems. In 2004, a breach in a slurry wall section caused significant leaking into the I-93 tunnel, prompting investigations of construction practices.

Far more serious was the collapse in July 2006 of concrete ceiling panels in a tunnel connecting to the turnpike, which killed a motorist, Milena Del Valle. The National Transportation Safety Board found that the epoxy anchors used to hold the panels had gradually pulled out under sustained load, and cited the selection of an unsuitable epoxy and inadequate oversight. The tragedy led to inspections, repairs and legal settlements, and it remains a sobering part of the Big Dig’s story.

Weighing the Results

Once complete, the tunnels removed the elevated artery from downtown and reconnected neighborhoods and the waterfront at street level. Traffic patterns changed, though how much congestion improved over the long term is still debated. The land freed above the tunnel became the Rose Kennedy Greenway, a story told in its own right elsewhere in these pages.

Building the Next Boston

The Big Dig showed how hard it is to rebuild a city without stopping it. Boston keeps reinventing itself anyway, one difficult, disruptive project at a time.

Quick check: What technique did Big Dig crews use to build underground walls before excavating the downtown tunnel?

  1. Slurry walls
  2. Timber cofferdams
  3. Open-pit blasting
Show answer

A. Slurry walls were formed in deep trenches held open with bentonite slurry, then filled with concrete and steel before the main dig began.

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The institutional news desk of the Boston Made network. Reporting is researched from wire services including The Associated Press and local sources, and written by the desk.

Boston History

Ether Day, 1846: The Boston Operation That Changed Surgery Forever

On October 16, 1846, in a surgical amphitheater at Massachusetts General Hospital, dentist William T. G. Morton anesthetized patient Gilbert Abbott with ether while surgeon John Collins Warren removed a tumor. It was the first widely publicized demonstration of surgical anesthesia.

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Amber glass bottles

Before the mid-1800s, surgery was a horror. Patients were held down, sometimes given alcohol or opium, and surgeons worked as fast as they could while patients screamed. Many people refused operations that might have saved their lives, preferring to risk the disease rather than face the knife. On a Friday morning in October 1846, in an operating theater at Massachusetts General Hospital in Boston, that began to change. This feature tells the story of Ether Day.

The Setting: A Room Under a Dome

Massachusetts General Hospital had opened in 1821 in a granite building designed by Charles Bulfinch. At the top of the building, beneath a dome, was a steeply tiered surgical amphitheater where students and physicians could watch operations. The room had good natural light from the dome, which was important in an era before electric lighting. After 1846 it would become known as the Ether Dome.

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The Dentist: William T. G. Morton

William Thomas Green Morton was a young Boston dentist. Dentistry involved painful procedures, and pain discouraged patients. Morton had been interested in ways to reduce it. He had worked with Horace Wells, a Hartford dentist who had tried nitrous oxide, or laughing gas, in a Boston demonstration in 1845 that was judged a failure when the patient cried out.

Morton turned to sulfuric ether, a chemical that was known to cause unconsciousness and was sometimes inhaled recreationally at “ether frolics.” Encouraged in part by advice from the chemist and physician Charles T. Jackson, Morton experimented with ether on animals and on himself, and in September 1846 he used it to extract a tooth from a patient without pain. He then sought a chance to demonstrate it at the hospital.

The Surgeon: John Collins Warren

John Collins Warren was the senior surgeon at Massachusetts General Hospital and one of its founders. He was about sixty-eight years old, highly respected and cautious about unproven claims. He had seen supposed painkilling methods fail before. Nevertheless, he agreed to let Morton try his preparation during an operation.

The Patient: Gilbert Abbott

The patient was Edward Gilbert Abbott, a young man, often described as a printer, who had a vascular tumor on the left side of his neck, below the jaw. Removing it would normally have been a painful operation performed on a fully conscious patient. Abbott agreed to be the subject of the demonstration.

October 16, 1846: The Operation

On the morning of October 16, physicians and medical students filled the amphitheater. Warren and his colleagues were ready, and Abbott was in the operating chair. Morton was late. He had been working with an instrument maker to finish a glass inhaler for administering the ether. According to accounts of the day, Warren was about to proceed without him when Morton arrived.

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Morton had Abbott breathe ether vapor through the inhaler. After a few minutes, Abbott appeared to be unconscious. Morton reportedly told Warren that his patient was ready. Warren began the operation, cutting into the neck and tying off the tumor’s vessels. Abbott did not cry out or struggle in the way patients normally did. Witnesses noted that he moved and murmured somewhat, but he showed none of the agony that everyone in the room expected.

When the operation was over, Abbott was asked what he had felt. He reportedly said that he had felt no pain, only a sensation like his neck being scratched. Warren then turned to the audience and, according to the traditional account, said, “Gentlemen, this is no humbug.” The phrase became famous because skeptical physicians had seen many supposed miracles turn out to be humbugs.

The Next Steps

A second demonstration the following day, in which the surgeon George Hayward removed a tumor from a woman’s arm, also succeeded. Within weeks ether was being used in other operations at the hospital, including a leg amputation.

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Henry Jacob Bigelow, a young surgeon who had witnessed the demonstrations, published a report in the Boston Medical and Surgical Journal in November 1846. His article spread the news to physicians across the United States and to Europe. By the end of 1846 and early 1847, ether was being used in operations in London, Paris and elsewhere.

The physician and writer Oliver Wendell Holmes Sr. suggested in a letter to Morton in November 1846 that the new state be called “anaesthesia,” from Greek words meaning without sensation. The term stuck.

Secrecy and Controversy

At first, Morton tried to keep the nature of his preparation secret, calling it “Letheon” and seeking a patent. Hospital physicians objected to using a secret remedy, and Morton eventually disclosed that it was ether. The question of who deserved credit for discovering anesthesia, Morton, Jackson, Wells or the Georgia physician Crawford Long, who had used ether earlier without publicizing it, became one of the bitterest priority disputes in medical history. That fight is a story of its own.

Remembering Ether Day

The Ether Dome still exists in the Bulfinch Building at Massachusetts General Hospital and is preserved as a National Historic Landmark. It contains a painting of the operation and other historical displays. In the Boston Public Garden, the Ether Monument, dedicated in 1868, commemorates the discovery of anesthesia. October 16 is still marked in medicine as Ether Day.

A Breakthrough Born in Boston

One morning in a domed room in Boston turned surgery from a desperate last resort into something patients could survive and endure. Medical breakthroughs remain part of the city’s identity, and they are one of the main ways Boston keeps reinventing itself.

Quick check: Who was the patient in the October 16, 1846 ether demonstration at Massachusetts General Hospital?

  1. Edward Gilbert Abbott
  2. Henry Jacob Bigelow
  3. Horace Wells
Show answer

A. Edward Gilbert Abbott, who had a tumor removed from his neck while anesthetized by Morton, reportedly feeling only a scratching sensation.

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Boston History

The Salem Witch Trials of 1692: What Happened, and Why It Still Matters

In 1692, accusations of witchcraft in Salem Village led to the deaths of 25 people. Here is how the crisis unfolded, how it ended and why its lessons still resonate.

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A black and white photo of an old church in Salem

In the winter of 1692, two girls in the household of a minister in Salem Village, Massachusetts, began behaving strangely. Within months, accusations of witchcraft had spread across Essex County and beyond, more than two hundred people had been accused, nineteen had been hanged, one man had been pressed to death and several others had died in jail. The Salem witch trials lasted less than a year, but they became one of the most studied episodes in American history and a lasting symbol of what can happen when fear overrides justice.

Salem Village in 1692

Salem Village, now the town of Danvers, was a farming community separate from the busier port of Salem Town. It was a place of tension. Villagers argued over land, boundaries and whether the village should be independent of the town. They were bitterly divided over their minister, Samuel Parris, who had arrived in 1689.

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The wider colony was also unsettled. Massachusetts had lost its original charter in 1684 and was operating without a secure government while awaiting a new one. Frontier warfare with French and Native forces in Maine had brought refugees and fear. These conditions did not cause the trials on their own, but they created an atmosphere of anxiety.

The First Accusations

In January and February 1692, Parris’s nine-year-old daughter, Elizabeth, and his eleven-year-old niece, Abigail Williams, began suffering fits, contortions and outbursts. A local doctor reportedly suggested that the cause might be witchcraft.

Under pressure, the girls named three women: Tituba, an enslaved woman in the Parris household; Sarah Good, a poor woman; and Sarah Osborne, an elderly woman who rarely attended church. All three were outsiders in some way. When questioned, Tituba confessed and described a conspiracy of witches, a statement that fueled fears that more were at work.

The Crisis Spreads

Other young women and some adults began reporting afflictions and naming accused witches. The accusations soon reached respected church members, including Martha Corey and Rebecca Nurse, a widely admired elderly woman. Accusations spread to Andover, Topsfield, Ipswich and other communities. In total, more than two hundred people were accused.

The Court of Oyer and Terminer

In May 1692, Sir William Phips arrived from England as governor under the new charter. Faced with crowded jails, he established a special Court of Oyer and Terminer to hear the cases. Lieutenant Governor William Stoughton served as chief justice. Several of the judges were prominent Boston men.

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The court accepted evidence that later generations regarded as deeply flawed:

  • Spectral evidence, testimony that the accused person’s spirit or shape had appeared to and tormented a victim, which the accused could not disprove.
  • Behavior of the afflicted in the courtroom, who sometimes appeared to suffer fits when the accused was present.
  • Physical examinations for supposed marks of witchcraft.
  • Confessions, often obtained under pressure. Those who confessed were generally not executed, which created a perverse incentive.

The Executions

Bridget Bishop was the first person hanged, on June 10, 1692. Further executions followed in July, August and September. In total, nineteen people were hanged. Among them were Rebecca Nurse, John Proctor and the Reverend George Burroughs, a former minister of Salem Village. In 2016, researchers confirmed that the executions took place at a site known as Proctor’s Ledge, where a memorial now stands.

Giles Corey, an elderly farmer, refused to enter a plea. Under the law of the time, he was subjected to pressing with heavy stones to compel him, and he died in September 1692. Several other accused people, including infants and adults, died in the harsh conditions of jail.

Doubts and the End of the Trials

As the accusations reached prominent people, and as more ministers questioned the reliance on spectral evidence, opinion shifted. In October 1692, Increase Mather, a leading Boston minister, presented arguments that came to be known as Cases of Conscience, cautioning that it was better for guilty witches to go free than for an innocent person to be condemned. Governor Phips, whose own wife was reportedly among those accused, dissolved the special court that month.

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Remaining cases were heard in 1693 by a newly established Superior Court of Judicature, which limited spectral evidence. Few convictions resulted, and those convicted were reprieved. Phips eventually released the remaining prisoners.

Apology and Reversal

The aftermath unfolded over centuries:

  1. 1697: Samuel Sewall, one of the judges, stood in his Boston church, the Old South Meeting House, while a statement was read accepting blame and shame for his role. The colony also held a day of fasting and reflection.
  2. 1706: Ann Putnam Jr., one of the principal accusers, publicly apologized, saying she had been deluded.
  3. 1711: The legislature reversed the convictions of many of the accused and provided compensation to some families.
  4. 1957 and 2001: Massachusetts passed further measures clearing the names of others who had been convicted.
  5. 2022: Elizabeth Johnson Jr. became the last of those convicted to be formally exonerated.

Why Did It Happen?

Historians have offered many explanations, which are not mutually exclusive. Some have emphasized local disputes and factional divisions within Salem Village. Others highlight the fears produced by frontier warfare. Others focus on religious beliefs about the devil, the vulnerability of women and outsiders, and a legal system that allowed unreliable evidence. Medical theories have also been proposed, though they remain debated.

Why It Still Matters

The trials endure as a warning about the dangers of panic, scapegoating and abandoning fair procedures. Arthur Miller’s 1953 play The Crucible used them to explore the climate of his own time, and the phrase “witch hunt” has entered everyday language. The episode underscores the importance of reliable evidence, the presumption of innocence and the courage to question popular fears.

A Lesson the Region Carries Forward

Massachusetts spent more than three centuries correcting the injustices of 1692. That long reckoning is itself part of how Boston and its region keep reinventing themselves: by confronting the past honestly.

Quick check: What type of evidence, widely accepted by the 1692 court, was later discredited?

  1. Written contracts
  2. Spectral evidence
  3. Fingerprints
Show answer

B. Spectral evidence, claims that an accused person’s spirit had tormented a victim, could not be disproved and was later limited by the courts.

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Boston History

The Big Dig, Revisited: How Boston Buried a Highway and Built a Greenway

Two decades after the elevated Central Artery came down, downtown Boston is a different city. A look at what replaced the highway, how neighborhoods reconnected and what other cities have learned.

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Clash of Empires: How a Global War Changed Boston Forever

For nearly half a century, the elevated Central Artery was the dominant feature of downtown Boston. Opened in the 1950s, the green-painted steel highway sliced between the financial district and the waterfront, cast long shadows over the streets below and walled off the North End from the rest of the city. Its replacement, the Central Artery/Tunnel Project better known as the Big Dig, is famous for its engineering, delays and cost, which are covered in a separate Chronicles feature. This piece looks at what happened after the highway came down: how the land was used, how neighborhoods reconnected and what lessons other cities have taken from Boston’s experience.

The Day the Shadow Lifted

The underground highway opened in stages in 2003, and crews then dismantled the elevated structure. As the steel came down, people saw downtown views that had been blocked for decades. Sunlight reached streets that had been in shadow. The noise of traffic overhead disappeared. For many longtime Bostonians, simply walking from Faneuil Hall to the harbor without passing under a highway was a revelation.

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The removal left a long strip of land above the tunnels. What to do with it became one of the most important planning decisions in the city’s modern history.

Choosing Open Space

Planning for the corridor had been underway for years. Many proposals were debated, including buildings, cultural institutions and commercial development. In the end, most of the surface land was dedicated to open space, an outcome shaped by earlier commitments, community advocacy and the practical limits of building over tunnels. The result was the Rose Fitzgerald Kennedy Greenway, which opened in 2008. The parks’ design, art and programming are explored in their own Chronicles feature.

The decision to prioritize parks over buildings had lasting effects. It created a continuous public space stretching through some of the most valuable real estate in the region, a choice that was controversial at the time and is still debated in specific cases.

The North End Reconnected

No neighborhood felt the change more than the North End. For decades, the elevated highway and its ramps had cut the historic Italian American neighborhood off from downtown. Reaching Haymarket, City Hall or Faneuil Hall meant walking under the dark structure or through underpasses.

With the highway gone, the North End’s edge opened up. Hanover Street, one of its main thoroughfares, once again connected more directly toward downtown. Visitors flowing along the Freedom Trail between Faneuil Hall and the Paul Revere House and Old North Church found the route more inviting. Restaurants and businesses along the neighborhood’s edge gained foot traffic, and residents gained easier access to the rest of the city.

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The Waterfront Rediscovered

The downtown waterfront had also been isolated by the highway. Long Wharf, Rowes Wharf, the New England Aquarium and the ferry terminals were physically close to the financial district but felt separate. Once the barrier was gone, the walk from the office towers to the harbor became short and pleasant.

The Harborwalk, a public walkway along Boston’s shoreline that the city has been extending for years, benefited from the improved access. People could walk from downtown to the water, then follow the harbor’s edge for long distances. The waterfront’s identity shifted from a place you drove past to a place you went.

Real Estate and Investment

Removing the highway made adjacent property more desirable. Buildings that had faced a highway now faced parks. Over the following years, new residential, office and hotel projects rose near the Greenway, and older buildings were renovated. Economists and planners have studied these effects, and many have concluded that the project contributed significantly to downtown property values and development, though isolating its exact impact from broader economic trends is difficult.

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Rising values also brought familiar questions about affordability, displacement and who benefits from public investment. These debates are part of the story, as they are in many cities that improve their public realm.

Other Changes Above Ground

  • The Leonard P. Zakim Bunker Hill Memorial Bridge, built as part of the project, became a new symbol of the city’s skyline.
  • Excavated material from the tunnels was used in several places, including the reshaping of Spectacle Island in Boston Harbor into a park.
  • Surface streets along the corridor were rebuilt, with new crossings and sidewalks, though some critics argue the roads alongside the Greenway remain too wide and difficult for pedestrians.

Lessons for Other Cities

Boston was not the only city to rethink an urban highway. San Francisco removed its elevated Embarcadero Freeway after it was damaged in the 1989 Loma Prieta earthquake, reopening its waterfront. Seoul removed an elevated highway and restored the Cheonggyecheon stream in the 2000s. Other American cities have since studied or carried out highway removal or capping projects.

Planners often draw several lessons from Boston:

  1. Removing a barrier can reconnect neighborhoods and transform how people move through a city.
  2. Burying a highway is extraordinarily expensive. Many cities have opted for cheaper approaches, such as replacing highways with boulevards rather than tunnels.
  3. Planning for the surface matters as much as the engineering. Decisions about land use, maintenance and programming determine whether new space succeeds.
  4. Long-term funding is essential. Parks need ongoing money for care and programming, which Boston has worked to secure through a mix of sources.
  5. Community involvement shapes outcomes. Neighborhood advocacy influenced what was built and how it serves residents.

A Downtown Transformed

Twenty years on, it is hard for younger Bostonians to picture the old elevated highway. The Big Dig’s legacy is not just the tunnels beneath the city but the reconnected neighborhoods and waterfront above them. It is one of the clearest recent examples of Boston tearing down part of itself and building something better in its place.

Quick check: Which neighborhood was most directly reconnected to downtown when the elevated Central Artery came down?

  1. The North End
  2. Back Bay
  3. Jamaica Plain
Show answer

A. The elevated highway had cut the North End off from downtown; its removal reopened streets and walking routes.

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