Several million Mexicans work in the Maquilladoras
US President Bush and his Mexican counterpart, Vicente Fox, are holding their second summit on Wednesday, with many hoping environmental issues are high on the agenda.
Significantly, President Bush's first overseas visit after his election was made to the Mexican president. America's poor southern neighbour is now its second biggest trading partner.
The mostly US-owned factories have spread along the border using cheap Mexican labour - and it is now claimed they are ruining the environment.
'El boom'
At the Maquilladoras, trains and lorries can be seen endlessly hauling materials south and manufactured materials north.
Mexico's economy has come to depend totally on the US, and the Maquilladoras have brought what border towns like Tijuana call "el boom" - to the pride of the man who founded the first of them, Enrique Maer y Tran.
"It's about five thousand companies that now exist in Mexico. There's three million... working in the Maquilladora business in the whole country, so it's a big business now, " he said.
Tijuana is the television capital of the world, churning out sets for all the top brands.
Workers here are internal migrants. Back home, they would work in the fields for much less than Isabel Martinez earns at Samsung.
"I get $80 a week, enough to send to my mother for the family," she said.
The rate is still a fraction of what companies would have to pay in America. No surprise then that Mr Bush made Mexico his first presidential visit, even courting them in Spanish.
'Sucked dry'
Mexico courts the Maquilladoras too, with cheap land, power and water. But "el boom" has seen Tijuana double in size fast, and stretch precious resources beyond the limits.
Hydrologist Oscar Romo says the river bed of the Tecate River has been sucked dry by industry.
"It's a tragedy for us because the river used to flood this area... now it's gone," he said.
"We're competing, the citizens against the industry, perhaps the industry will win."
Lawyer Cesar Luna is fighting foreign factory bosses over another threat.
He points out broken barrels of waste left after a company set up to salvage car batteries and then folded.
"This is a classical example of an irresponsible foreign American company doing business, leaving an environment of catastrophe and just going back to the United States and effectively shielding himself from any liability possible," he said.
"Now, Mexico doesn't have the funds or the proper infrastructure to clean this up."
'El bust'
There is also a price of 'el boom' being paid by Maquilladora workers.
Families who have flocked here from all over Mexico are washing or cooking out on the hillside.
They are scraping by without power, schools or healthcare in the hope of a regular pay cheque from the Maquilladoras.
These workers are just starting to share another worry - that if America's current economic slowdown turns into full-blown recession, the jobs which brought this great influx will go, and then "el boom" could become "el bust".
Whatever his White House summit yields, Mexico's president must also look to the long term and how his country should step out of the shadow of its big industrial brother.