The Detroit skyline under the Ambassador Bridge. (Carlos Osorio/AP)

Every year, $100 billion in trade passes back and forth between the United States and Canada here — roughly 16.5 percent of the total annual trade between the two countries. And it all trundles across the traffic-impaired and slowly declining 86-year-old Ambassador Bridge.

The Ambassador’s questionable condition — concrete chunks rained down upon the Canadian side last year — has trade experts concerned that a vital route could come to an unexpected halt. Truck companies, meanwhile, decry delays that can make crossing a bridge of less than two miles a four-hour hassle.

Canada promises to solve all of that with its $2.1 billion planned Gordie Howe International Bridge, which would begin construction within the year and open in 2020. Canada touts it as its single biggest infrastructural priority. And it has the added emotional pull of being named after the beloved Howe, a Canadian ice hockey legend who played for the Detroit Red Wings for 25 seasons, and who died last month at age 88.

But the new expanse would bring bitter defeat to the wealthy Michigan family that owns — and profits heavily from — the Ambassador. And it is not giving up without a fight.

The Moroun family — led by 89-year-old patriarch Manuel “Matty” Moroun — has owned the Ambassador since 1978. Moroun runs a diverse portfolio of holdings, including insurance, railroads and real estate companies, that keeps him ranked among the richest men in the United States.

He’s known for a bare-knuckled approach to business. He once spent a night in jail in 2012 after a judge found that he had failed to make promised access improvements to the Ambassador.

More recently, the Morouns have been pulling every lever to stall the Gordie Howe, including litigation challenging the approval process for the bridge and asserting their singular right to operate a bridge traversing the two countries. So far, the courts have dismissed these suits, including one two weeks ago, in which a federal judge found that contrary to the Morouns’ claims, “the crossing agreement was neither arbitrary, capricious, an abuse of discretion nor unlawful.”

But the Morouns also countered by buying up parcels of property in Detroit that would be needed for the Canadian project to finish. Michigan should have no trouble taking back the land through eminent domain, but it’s a process that could take years.

It’s clear why the Morouns are battling so hard: One study released in 2008 by the Detroit River International Border Crossing Group estimated the Ambassador would lose 75 percent of its toll revenue with the opening of the Gordie Howe. It’s unclear precisely how much revenue that is, though that same study estimated that the Gordie Howe would generate $70 million annually for Canada.

“The bottom line is that there has to be a better, collaborative solution,” said Mickey Blashfield, spokesman for the Morouns’ Detroit International Bridge Co.

The Ambassador Bridge, the only privately owned border-crossing bridge connecting the United States and Canada, is a relic of the heady days of the pre-Depression 1920s, when money could move mountains and, in this case, build bridges. As trade picked up in the 1920s, a need for a bridge became clear. But when neither government could get a project off the ground, a wealthy banker named Joseph Bower secured all the proper permits, brought two international entities together and formed the Detroit International Bridge Co.

The Bowers sold it to the Morouns, who dodged an attempt by Warren Buffett — who owned a 25 percent stake in the company — from buying it. But they are having a difficult time defending the Ambassador from charges that it is unequipped to handle the traffic that pours onto it, and that a significant alternative route is essential to protect the flow of trade.

“Ohio’s economy would be brought to its knees, and the impact would ripple out from there into the Deep South” should the trade route be halted for any reason, said William P. Anderson, director of the Cross-Border Institute at the University of Windsor.

“The Ambassador needs to be replaced,” said Anderson, who can watch the trucks crawl across the bridge from his warren of offices overlooking the Detroit River.

While piecemeal improvements to bridge access have been made on the U.S. side in recent years, traffic going into Windsor gets funneled onto busy Huron Church Road, which frequently clogs with truck traffic. The road is hemmed in by motels, strip malls, the occasional Tim Horton’s and other gulps of Canadian culture for 2.5 crawling miles until, mercifully, all that traffic merges onto the King’s Highway 401, Ontario’s busiest freeway, and head toward Toronto or other points east. Westbound truckers have to endure the same gantlet in reverse.

“If something happens to the Ambassador Bridge, there is a huge percentage of Ontario’s economic output that is hit,” said David Cree, president and chief executive of the Windsor Port Authority.

The Moroun family contends that the Blue Water Bridge, connecting Ontario with Port Huron, Mich., and more than an hour away, provides plenty of backup for the Ambassador. They also point to the Detroit-Windsor Tunnel, which connects the two cities under the Detroit River, though that doesn’t allow trucks.

The real effort should be to “upgrade what you do have” and make improvements to the Ambassador, Blashfield said.

To that effect, the Morouns have been seeking permits and approval to build their own alternative for the Ambassador: a new bridge that would run parallel to it and would allow the Ambassador to close for a time for repairs and improvements. If the Morouns get their way, they’d then be running two “Ambassador Bridges” while the Gordie Howe gets mothballed.

The second, as-yet unnamed Moroun bridge, did receive approval by the U.S. Coast Guard, but still faces scrutiny by the Michigan Department of Natural Resources and U.S. National Park Service. It also would need the support of Canadian authorities, who have already raised numerous concerns.

The Gordie Howe, meanwhile, offers other upsides, aside from a faster alternative route.

The bridge would connect Windsor to the Detroit neighborhood of Delray, a once-bustling enclave with a vibrant Hungarian culture that has become a blighted, decaying shell of itself, dotted with abandoned warehouses, vacant lots and boarded-up homes. But advocates believe the bridge could transform the neighborhood through 150 acres of green spaces, bikeways, shops and customs facilities, all funded by Canada.

Blashfield, the Moroun spokesman, has questioned the legality of such an arrangement. But Jeff Cranson, a spokesman for the Michigan Department of Transportation, said there was nothing particularly unusual about it, calling it similar to the way the original Blue Water Bridge was financed in 1938.

The tug-of-war over who can build the better bridge has brought the blight that pockmarks Detroit across the river to Windsor. Neighborhoods of tidy residential homes near the University of Windsor sit abandoned and boarded-up like an eerie Love Canal. The Morouns have purchased dozens of homes at the base of the bridge in hopes of using the land for a planned plaza area around the bridge.

Those homes have been allowed to decay, and residents blame the Morouns for creating a blight and lowering property values.

“They are lot-busting,” said Mary Ann Cuderman, a critic of the Morouns, referring to their practice of buying up and boarding up.

The city won’t allow the Morouns to destroy the buildings for fear it would end up slowly driving everyone else from the neighborhood. So a standoff — and legal action on both sides — continue.

Even the National Park Service finds itself entangled in the bridge morass. It owns a prime piece of riverfront land in Detroit that the Marouns would need to complete their new bridge. The Morouns would like to trade an adjacent piece of land with the Park Service, but the agency has not given final approval for this.

Meanwhile, those who use the Ambassador more than anyone — truck drivers — are anxious for an alternative. The frequent bottleneck has fueled a persistent joke among truckers along the lines of: You can drive from Montreal to Miami and only hit 17 stoplights. And all 17 are in Windsor, Ontario.

Philip Fracassi, president of Cole Carriers, has a fleet of 150 trucks, with 60 of them crossing the Ambassador on any given day carrying automotive components crucial to the industry.

Fracassi estimated that his company pays up to $700,000 annually in tolls to the Morouns. But that isn’t the real issue, he said.

“What really is the issue is time,” he said, explaining that his drivers are paid by the hour. “Our drivers are limited in hours of operation.” And a three- or four-hour delay on the Ambassador Bridge, he said, is common now.