5 p.m. Laredo International Airport
People flying commercially in and out of Laredo have no choice but to take prop planes. Only the most important cargo flies on a jet. Each night, DC-8 cargo planes swoop in and out, carrying everything from auto parts to medical supplies, usually because someone needed them yesterday. Companies routinely ship entire planeloads of gear when an assembly line is shut down for want of some crucial piece that's made or imported here. "Sometimes I've seen an invoice for, say, hubcaps, where the value of $1,000 or so is less than the cost of shipping," says Lucy Santos Wright, a freight forwarder. Of course, that's not all that arrives. Later this night, 215 lbs. of marijuana are found in an Emery Worldwide package marked for Saturday-morning delivery to a Michigan town. By itself, Laredo is the nation's busiest land port; the Laredo airport is the seventh busiest Latin port of any kind.

6 p.m. Unitec Industrial Park
Father Francisco Munoz stands in front of two red, green and white tractor trailers and says a blessing. That's standard procedure for any new building, but this one is special. It's the grand opening of Consolidated Freightways' 20-acre compound and 51,000-sq.-ft. warehouse. The company loads an average of 60 trailers a day bound for Los Angeles; Detroit; Salt Lake City, Utah; and Memphis, Tenn. Concrete crews are pouring a million square feet of warehouse a month on Laredo's red-hot north side. The soft-spoken priest asks his audience to think about "who we are and how we are, as we move from one place to another." And then the guests drink margaritas and devour a cake decorated with a toy truck.

9 p.m. World Trade Bridge
Rush hour has arrived. In the first five minutes, 27 trucks leave Mexico and pull into the Customs checkpoint. One by one, the drivers wait to be processed, reading Spanish newspapers and comic books or talking on their CB radios. Eleazar Camancho Luna, 21, listens instead to Latin disco music. He makes five crossings a day — $20 for full loads, $15 for empty trailers that need to be returned — and works six days a week. Not bad for a single guy, he says. The Mexican trucks are serviceable but spare: Luna's lacks the global-positioning systems found in some U.S. rigs, or even air conditioning. For years Mexican truckers were permitted to drive only 20 miles into the U.S. before transferring their loads to American haulers. But a NAFTA panel ruled last February that the U.S. must soon allow Mexican trucks access to the whole country. U.S. truckers say the Mexican rigs aren't safe — and the drivers aren't qualified.

Luna isn't going very far anyway. After a Customs inspector waves him through, he lets out a sigh of relief. He can drop off the 44 tons of iron towers and still get back home tonight.

10 p.m. Laredo Wal-Mart
Most of the 500 cars in the Wal-Mart parking lot have Mexican plates — about normal for a Friday night. Laredo boasts the highest-grossing Wal-Mart per square foot in the U.S., because this town of 200,000 is really a market for more than 1 million people. Right up the highway from the big downtown bridge, the store is often a first stop for visiting Mexicans. Inside, you can find Fabuloso detergent, table runners decorated with images of the Virgin of Guadalupe, and CDs featuring popular Norteño and Tejano stars. The biggest selling items are aluminum foil, toilet-bowl cleaner and three-packs of paper towels. Store manager Ed Garza says traffic in the store picks up as midnight approaches: " People like to shop when it's cooler."

11 p.m. Old Downtown Bridge
A maintenance man takes advantage of the lull to mop the tile floor in the narrow walkway that funnels pedestrians from Mexico into downtown Laredo. Customs supervisor Greg Salinas expects the traffic to pick up in a few hours, when the borrachos come over, the drunks and Friday-night revelers who have been enjoying the Nuevo Laredo night life, some even venturing to Boystown, the red-light district, where prostitutes have held court for generations of Texas fraternity boys, roughnecks and cowboys. The revelers will buy tequila and six-packs of Corona at half the U.S. price on the Mexican side and bring it back across.

11:51 p.m. World Trade Bridge
The last semi, No. 3,902 for the day, reaches the checkpoint of the World Trade Bridge. Its load: 45 pieces of wrought-iron furniture, headed for the patios of the North.

— With reporting by Hilary Hylton/Laredo