RIO GRANDE CITY, Tex. — Caught quite literally in the middle of the international debate over the way the United States trades with its southern neighbor are two Texans named Sam.
Sam Vale and Sam Sparks Jr. own two bridges that stretch across the Rio Grande, connecting farmers on either side with markets on the other, and linking communities in South Texas and northern Mexico that sometimes meet in the middle.
The majority of border bridges belong to the government. But the Sams are exceptions, private owners of crossings collecting tolls that can exceed $30 per truck.
As cross-border truck volume doubled in the last two decades, those tolls have given rise to a pair of multimillion-dollar businesses, a dividend of the traffic ferrying construction materials in both directions, avocados from Mexican fields to American supermarkets, and Midwestern wheat to Mexican breweries.
“We used to joke that if you want to own a bridge, you have to be named Sam: Sam or Uncle Sam,” said Mr. Vale, who owns a two-lane crossing in Rio Grande City, a bit more than an hour’s drive from Mr. Sparks’s four-lane roadway. Both men are second-generation bridge owners.
But now their unique revenue stream could be in jeopardy.
The Trump administration wrapped up a fifth round of wrangling over the North American Free Trade Agreement, or Nafta, this week in Mexico City. President Trump has pursued an aggressive rewrite, pushing to protect American workers and stem the flow of goods from Mexico.
The focus on trade is exposing cracks of tension between the president and a constituency otherwise aligned with his economic instincts.
Major retailers and manufacturers are mobilizing to keep the deal alive and to protest rules that could make it more expensive to bring parts and products in from Mexico. For the bridge moguls, anything that stanches the flow of traffic could be costly.
Trucks carried $373 billion in cargo across bridges on the southern border last year, accounting for 71 percent of all trade in goods with Mexico, according to the American Trucking Association.
“Nafta benefits this bridge big time,” said Mr. Sparks, who voted for Mr. Trump. “We kind of want them to leave it alone.”
Mr. Sparks and his three siblings own the Progreso International Bridge, serving Progreso, Tex., a town blanketed by ranches and farmland. A border wall built on American soil runs through his property, and he can open it by punching a code into a keypad on its facade.
The bridge is a study in a trade deal that has been a boon to some American farmers and hurt others. For American corn, Progreso is one of the busiest exit points in the country. Nafta was a windfall for American grain producers, who have more efficient operations than their Mexican counterparts.
It’s a different story for watermelons and onions, which are trucked in from the depths of Mexico, filling the northbound lanes of Mr. Sparks’s bridge on their way to American stores. Fresh fruit and vegetable harvesters in the United States complain about competition from a neighbor that can grow some crops year-round and pay farmhands much less.
Mr. Sparks would like to see more trucks going south on his bridge, but he sees the give-and-take as unavoidable.
“We export a lot of products through our bridge, and we get paid a toll, and we want that to continue,” Mr. Sparks said. “But to do that we need fair trade. Mexico has to benefit from that. Canada has to benefit. If everyone is getting a good deal, it just works.”
Beyond the truck traffic, the town of Nuevo Progreso, at the southern end of Mr. Sparks’s bridge, has found creative ways of cashing in on its proximity to Americans. There are abundant taco shops, tequila that can be bought and consumed in the streets, and many, many dental clinics. More than 100 dentists’ offices cater to an American clientele seeking fillings and root canals at a fraction of the cost at home, along with 80 pharmacies offering pills and medical treatments at a cut rate. The attractions draw more than 800,000 pedestrians across Mr. Sparks’s roadway every year, at a cost of 50 cents apiece.
Some of them meet in the middle.
Maria Maldonado lounged on a bench atop the bridge’s walkway on a recent afternoon, facing a placard that announces the spot where Mexico ends and the United States begins. Ms. Maldonado, 33, lives in Nuevo Progreso and works in a taqueria there. She was waiting to meet her nephew, an American citizen who works as a carpenter 10 miles north of the border and has diabetes.
“He wants medicine,” she said, holding up two plastic bags, “and tortillas.”
Mr. Trump’s hard line on immigration could eventually slow foot traffic, experts say, by discouraging tourists from Mexico. But proposals on the Nafta negotiating table would more directly affect trucks and what they carried.
The administration has floated the idea of increasing the American-made content in goods traded through the pact and requiring renegotiation every five years. Mr. Trump said last month that the United States might end the deal altogether.
“Business loves certainty, and they aren’t getting any,” said Raymond Robertson, an economist at Texas A&M University. Border bridges, he said, are “ground zero for Nafta trade, so if you start reducing the U.S.-Mexico trade, it will hit them first.”
If it becomes expensive to send products north, Mexico could turn to one of the 45 countries with which it has free-trade agreements. Long the leading destination for American corn, Mexico has increasingly turned to suppliers in Brazil to hedge against Mr. Trump’s tough talk on trade.
“If Mexico diversifies, what are these bridge operators going to do?” Mr. Robertson asked.
It’s a good bet that Mr. Vale will survive. The 74-year-old took the reins of the Starr-Camargo Bridge around 1980, when it was an unremarkable passageway, handling cars and pickups traveling between two impoverished towns.
Then Nafta was signed in 1993, and the number of commercial trucks went from one a week to as many as 300 a day. Mr. Vale takes in around $4 million a year in tolls. (Mr. Sparks, 63, would not specify his revenue, but it is also in the millions.)
Mr. Vale has also pursued an array of ventures beyond the bridge. A column of eighteen-wheelers that were waiting to cross belongs to him, and so does the sand in them. He brought the dolomite limestone from a mine in Mexico, and it will travel to concrete producers and asphalt plants across South Texas, earning Mr. Vale millions each year.
He owns about 60 acres around the bridge, and a railroad that runs through the property and links to a Union Pacific line. He is paid to transport pipes, lumber and sheet metal on rail cars that come in from a town a few miles away, but still on the American side.
That mix of ventures has allowed Mr. Vale to indulge in some other pursuits. He drives a cherry red Mercedes-Benz drop-top with a license plate that reads “Cizzle.” He has nine black German shepherds — some of which were flown from Prague for breeding — that live in climate-controlled doghouses scattered across his properties.
“Central air and heat, insulated cedar-wood homes,” he said. “Everybody has them in Texas.”
Mr. Vale does not love leaving Texas, but he has made six trips to Washington since the election to make his case to lawmakers. His pitch is simple: “Don’t hurt the country, don’t hurt the businesses that support you, Mr. President. Don’t hurt the people who are critical to the economic survival of the United States.”