I was in the passenger seat of a Cole Carriers freight hauler driven by Al Prevett, a craggy and chatty fifty-five-year-old Canadian with spiky white hair and scuffed black steel-toe boots. He had been driving back and forth over the Ambassador for seventeen years. We swapped stories of bumper-to-bumper traffic, cross-border bargain hunting, and surly American immigration officers. Prevett recalled an agent stomping into his RV, inspecting the fridge, and confiscating a tomato and a green pepper. “You can take a whole truckload across if you have the paperwork, but you can’t just take one,” he said. “Still, I find the border treats you the way you treat it.”

We were headed to a warehouse in Detroit to fetch four 18,000-pound coils of flat steel, which we would bring back to Canada to be stamped into hoods, doors, and other car parts. “They expect us to be on time, but then you might sit there waiting for hours,” Prevett said. The job requires patience and efficiency. Some drivers — not him — wear adult diapers and take amphetamines to avoid stopping.

And then there’s handling the bridge itself, which is in bad shape. Riding up high in the truck, I could see the Ambassador’s condition as I had never been able to from my car. In some spots, the perimeter was lined with metal barriers; Prevett pointed out where the railings had rusted to flakes. There were holes in the curb so big you could see fishing skiffs bobbing on the waves below. Chunks of concrete, some almost two feet wide, had been known to drop from the underside. The bridge should accommodate four lanes, but repaving crews were there nearly every day, so it was now down to three.

Safety inspections have determined that the Ambassador, at eighty-eight years old, is safe enough. In an ideal world, it would be temporarily closed for repairs, but that is not an option. It is the fastest and cheapest route between the manufacturers on either side, and in 2016 truckers like Prevett used it to haul about $150 billion worth of goods — a quarter of all US-Canada trade. There is a tunnel under the river, but it’s too small for many tractor trailers. A truck ferry that scoots across the water can carry only 400 each day; it’s mostly used to deliver hazardous materials, which Michigan’s Department of Transportation won’t allow on the bridge. Taking the Ambassador out of commission would imperil thousands of American jobs.

There is another reason why the bridge has been left to deteriorate: it is the only major crossing into the United States owned not by a government but by a private company, which means that, as concerns go, it’s not apparent that public safety ranks above profit. There are 419 privately owned bridges in America (one of them is a pedestrian bridge between California and Mexico), but none are of the Ambassador’s size and importance.

Its owner, Manuel Moroun, is a ninety-year-old billionaire from Detroit who has devoted half his life and tens of millions of dollars to thwarting politicians who want to gain control of the border, and stymieing commercial competitors who want to break his monopoly. At age eighty-four he spent a night in jail for refusing to comply with a judge’s order that he complete ramps from the Ambassador to nearby expressways. He has donated to the campaigns of Michigan politicians and made alliances with unlikely bedfellows: Americans for Prosperity, the Koch brothers’ lobbying group; Detroit’s New Black Panther Party; and Jimmy Hoffa’s Teamsters. Moroun’s family corporations have sued or been sued dozens of times; bridge litigation alone has spawned some twenty cases. Bruce Heyman, who recently returned to the United States from a three-year post as ambassador to Canada, joked to me, “I had heard that just talking to him was reason enough for him to sue you, so I didn’t do that.”

There are many public officials in Detroit and Windsor who haven’t seen Moroun in years, or even met him. He avoids events and interviews (including with me), and it’s unclear how much power he has already passed to his heir, a forty-four-year-old son named Matthew (who also declined to talk). In pictures, Moroun looks like a squat, liver-spotted grandpa. A shopkeeper in Windsor told me, “He’s got this lively little face, with eyes like a leprechaun.”

Most people call him Matty. Forbes recently reported that he is worth $1.59 billion, but that is merely an estimate. In addition to the Ambassador — the tolls are believed to bring in about $60 million annually — he owns real estate operations, insurance firms, and customs brokerages. The family also runs several trucking companies, one of which made at least $700 million last year. Most of Moroun’s businesses are not listed on the stock market, so he has to share few details about what he does and earns. Headquarters is a converted middle school in suburban Detroit with no sign outside.

On paper, Moroun fits Donald Trump’s formula for infrastructure development, based on “unleashing private-sector capital and expertise.” He also reveals how problematic the result can be. The Ambassador is evidence that much can go wrong when public works belong to private owners — and beyond the bridge itself, the neighborhoods on each end have fallen into decay.

Prevett, who lives in Windsor, doesn’t have much choice but to keep driving across. We traversed the bridge without incident — there was nothing to declare or inspect on the empty trailer, and traffic that day was light. As we approached Michigan, however, he started to make me nervous. “When it’s packed on here, the whole thing starts to shake a little,” he said. He glanced over at me. “If it were really unsafe, I’ve got to believe they wouldn’t let us be driving over it.”