The cities along the Texas and Mexico border differ dramatically. Those in Texas are sprawling, while those in Mexico are buzzing with urban vibrancy. This is odd considering that many of these border cities have shared histories and cultures.

U.S. cities like Brownsville, McAllen, Laredo and El Paso are demographically similar to their counterparts in Mexico, yet look like classic American Sun Belt cities. Their downtowns are quiet, with automobiles outnumbering pedestrians; interior neighborhoods have single-family homes; and strip malls sprawl into the peripheries.

But walking across the bridges from these cities into Mexico is like entering another world. In cities such as Matamoros, Reynosa, Nuevo Laredo, Acuña and Juárez, suburban sterility gives way to an urban bonanza. Downtown areas, already far more compact, are dominated by public squares, pedestrian malls and commercial alleyways. Nearby residential density brings throngs of people into these spaces daily, generating an electric street vibe, as performers entertain large audiences, food stands line the sidewalks and Latin dance music thumps from storefronts.

These design contrasts result from both nations’ differing planning policies. While similar for centuries, a splintering largely occurred during the 20th century, says Daniel Arreola, an Arizona State University professor of urban planning. Before then, there were common threads that tied together Mexican and Texan cities: Many of these areas were settled by indigenous peoples and later colonized by the Spanish, who imported European design standards.

Mexico’s border cities preserved their European architectural features primarily, says Arreola, because they remained too poor to fund major redevelopments. But in Texas, the European influences were wiped out. Growing American wealth and a rising Anglo elite inspired urban “modernization,” both through top-down projects and code changes.

San Antonio, which is 63 percent Hispanic and a two-hour drive north of the border, is a prime example. Throughout the 20th century, new developments were added and old ones retrofitted to mirror common American planning guidelines -- the zoning code enforced separated uses; federal money helped the city replace old-style barrios with generic public housing; streets were widened and building setbacks enforced; and urban renewal money was used to raze neighborhoods for roads, parks and convention centers. Today, San Antonio looks nothing like a Mexican city, nor do other cities in Texas.

Interestingly, Mexico and the U.S. may invert these differences throughout the 21st century. Although the preservationist instinct “is beginning to seep into Mexico,” Arreola says, the country’s growing wealth will inevitably bring calls for American-style modernization. This has already happened in wealthy Mexico City, with its many highways and suburban developments. Meanwhile, U.S. cities, having already endured this demolition mentality, are experiencing renewed appreciation for dense, walkable neighborhoods. In this respect, the U.S. is rediscovering great designs that never disappeared south of the border.