Ciudad Acuna, across the Rio Grande from Del Rio, Texas, is at the midpoint of the 1,950-mile border between the United States and Mexico, making it a useful manufacturing hub even if it’s surrounded by endless scrub. The city is one of dozens of such industrial nerve centers in Mexico.

The first foreign factory came to Ciudad Acuna in 1969, and a stream of others followed. Today, 63 factories fill five industrial parks, employing 43,000 people. Workers here assemble Oster appliances, sew automotive air bags, build electric motors, sort supermarket coupons and carry out a myriad of other tasks.

They also assemble huge mining trucks with a 400-ton capacity for Caterpillar, the Illinois heavy equipment firm. Emerson, a Missouri-based industrial conglomerate, is scheduled to begin assembly operations here in a few weeks.

“We’ve grown 17,000 jobs in three years,” Mayor Alberto Aguirre Villarreal said. “We have the lowest crime rate along the border. This helps us. Companies that come don’t ask us, ‘What is the risk?’ ”

Acuna also has a history of antipathy toward unions, which officials consider a major selling point in attracting manufacturers.

“We’ve never had union issues. That’s been a great positive for us. We’re not used to having unions in our city,” said Jose Jorge Ramon, the director of economic development for the city.

Factory managers say that by keeping unions out and bringing workers in from southern Mexico, companies that operate here are able to keep wages low.

“These people come to work hard, to suffer. They are willing to work for very little,” said Roberto Rivero, a human resources manager at the Japanese-owned Takata plant here that employs 2,400 people to piece together automotive air bags.

No matter what one thinks of trade unions, Mexico’s are without a doubt different from those that operate in much of the world. Only a fraction have democratically elected leaders. Few actively bargain on behalf of their workers. During the 70 years of rule by Mexico’s Institutional Revolutionary Party, whose candidate is considered the leading contender to win Mexico’s presidential election July 1, unions became more of a tool for political control than one focused on workers’ rights.

Union leaders from other countries often view their Mexican counterparts with consternation. “Their reaction is, ‘These guys are from the mob.’ Pinkie rings, $3,000 suits. And a lot of these guys are in Congress,” said Ben Davis, the director of international affairs at United Steelworkers, the largest industrial labor union in North America.

Forty percent of Mexico’s 47 million workers are covered by union contracts, but few feel any benefits. “There are workers who don’t even know they belong to a union,” said Maria Xelhuantzi Lopez, an expert on collective bargaining at the National Autonomous University of Mexico.

Unions docile to demands from management, or firmly under the control of owners, have allowed the center-right governments of the National Action Party, which has controlled the country’s presidency since 2000, to promote the nation as a low-wage, owner-friendly destination.

“The Mexican case has become paradigmatic. It is in contrast to what is happening in Brazil and China, where wages are going up,” said Huberto Juarez Nunez, a labor relations scholar at the Meritorious Autonomous University of Puebla, a Mexican state best known for being home to a vast automotive-assembly industry.