At rush hour one June day in 2012, authorities held traffic over the Francis Scott Key Bridge while a transport ship passed underneath, delivering a set of 14-story super cranes that would herald a new era for the Port of Baltimore.

These gantry cranes were final pieces in a much-anticipated expansion of Baltimore’s Seagirt Marine Terminal. The port would soon be able to accommodate some of the newest — and biggest — cargo ships on the ocean.

“Either you have big cranes, or you’re out of business,” James White, then-executive director at the Maryland Port Administration told the Baltimore Sun that day, as he watched the cranes ferried into the harbor.

Just over a decade after Baltimore welcomed this new supersized breed of ship into its port, a 984-foot Singaporean vessel called the Dali arrived. The ship departed Seagirt early Tuesday and, under an hour later, plowed into the Key Bridge, toppling the 47-year-old structure in a matter of seconds and sending six construction workers to their deaths.

In the wake of the crash, structural engineers have only been able to speculate on whether any protection could have safeguarded the Key Bridge against such a powerful vessel. The Dali experienced simultaneous electrical and mechanical failures that caused its crew to lose control.

To bring in these behemoths, Maryland entered into a $1.3 billion, 50-year deal more than a decade ago with Ports America Chesapeake to manage the state-owned Seagirt terminal, dredge a deeper channel and bring in the four super cranes. The plan, which ushered in giants like the Dali at the Port of Baltimore, was cheered by politicians and port officials.

Since the first of these cargo ships set sail in the 1950s, their size has exploded — especially in the last 20 years, said Salvatore Mercogliano, a maritime historian at Campbell University.

“If you looked in 2000 at the size of ships, you would never guess where they’d be today,” said Mercogliano. “Now, we’re bringing ships the size of supertankers into downtown Baltimore.”

The world’s first container ship, which set out from New Jersey in 1956, was a converted oil tanker that could hold 58 containers. By the early 2000s, the capacity of container ships had exploded to carry just under 9,000 20-foot containers on the largest ship. .

By modern standards, the Dali is far from the biggest cargo vessel. The Singapore-flagged ship can hold almost 10,000 twenty-foot containers, less than half the capacity of the world’s biggest container carrier today. But Mercogliano said the question is not how the Dali compares to its peers, but how it would have stacked up to the ships coming into the Port of Baltimore when the Key Bridge was being built in the 1970s.

There’s no contest. When construction on the Key Bridge began in 1972, the biggest cargo vessels in the world weren’t even a third the size of the Dali.

Much of the recent growth has been triggered by the expansion of the Panama Canal, the Latin American shipping artery connecting the Atlantic and the Pacific oceans. New locks opened in 2016 that tripled the size of ships that could pass through the canal, giving rise to “neo-Panamaxes,” ships like the Dali so large they couldn’t have squeezed through the old Panama Canal.

Benjamin Schafer, a civil engineering professor at the Johns Hopkins University, said the Port of Baltimore brought on more risk when it began catering to these new-era ships.

“More mass means more energy means harder to stop,” he said. “That’s the most important thing.”

A typical highway bridge is designed to withstand a minimum of about 200 tons, already a lot of weight, Schafer explained. When fully loaded up, the Dali clocks in at around 116,000 deadweight tons, close to 500 times that standard capacity. On top of the Dali’s weight, the sheer size of the ship — its width and towering height — make it harder to guard against disastrous allision, Schafer said.

Some have argued in the wake of the Key Bridge collapse that the size of the Dali is beside the point. The Dali isn’t even the largest ship to enter the Port of Baltimore, and countless ships of its size have travelled safely beneath the Key Bridge in the last decade.

“The Dali incident has nothing to do with the fact that it’s a big ship,” said Walter Mitchell, a maritime analyst and consultant who spent his career working in Maryland. “Any number of smaller ships could have inflicted the same amount of damage with the same result.”

There’s also the warning a state engineer issued in 1980, after a 609-foot freighter toppled the Sunshine Skyway Bridge in Tampa Bay, killing 35 people. Neither Maryland’s Key Bridge nor the Chesapeake Bay Bridge could have withstood a direct hit from a similar ship, the transportation official acknowledged toThe Baltimore Sun at the time.

“It would knock it down,” he said. “Whatever unit got struck, that section would be knocked down.”

Still, Capt. Allan Post, executive director of Marine Education Support and Safety Operations at Texas A&M University, said this week’s tragedy raises questions about how we regulate our nation’s waterways. The Port of Baltimore is certainly large enough to accommodate ships this large, but elected officials will be asking in the coming months and years whether proper precautions have been taken, Post said.

“In this country there are certain roads that can’t take certain sized vehicles,” he noted. “Does the same thing apply to our nation’s waterways? How do we come to a consensus about what is an appropriate size?”

The issue isn’t just that ships have gotten larger, added Mercogliano, who hosts the YouTube show “What is Going on With Shipping?” In the age of one-click online shopping, Mercogliano said it’s almost like we’ve injected steroids into the global supply chain, with total cargo volumes growing exponentially since the first container ships set out to sea. More and more ships come into port each day, increasing the odds of incident.

In Baltimore, cargo traffic has more than doubled in the last two decades. In October of last year, the Port of Baltimore handled more than one million tons of cargo, according to Maryland Port Administration data, up from a little under 550,000 tons in the same month of 2002.

And these mega ships aren’t going anywhere, supply chain experts said.

In 2021, Seagirt welcomed four new cranes – even taller than the ones delivered in 2012 – part of a massive expansion plan to double the port’s container capacity, facilitated by a half-a-billion dollar rail tunnel project that will allow trains to stack containers on top of each other. The terminal now caters to even bigger, “ultra-large” ships, two of which can now dock there simultaneously.

Last August, the Port of Baltimore accepted its biggest ship on record: the roughly 15,000-unit Ever Max.

Baltimore didn’t start the arms race for bigger container ships; it merely opted in, noted Schafer, the Johns Hopkins engineer.

“From a policy standpoint, I’m thinking about, do we understand all the consequences of that?” he said. “We certainly reaped the benefits.”

Reporter Rona Kobell contributed to this story.