Gaps in the Border Wall

McALLEN, Texas—Republican presidential candidates are vowing to finish former President Donald Trump’s long-promised wall along the U.S.-Mexico border. But a host of issues—including securing land and navigating difficult terrain—makes it much more complicated than campaign promises make it sound.

The farther west you go along the southern border’s nearly 2,000 miles, the more likely you’ll encounter physical border barriers. Around 565—28 percent—of those 2,000 miles are on federal property, mostly in California, Arizona, and New Mexico.

But it’s different in Texas. 

There, private citizens hold the deeds to thousands of parcels along the Rio Grande, which comprises the U.S.-Mexico border in most places. Treaty provisions (a 1970 U.S.-Mexico treaty prevents barriers from obstructing the flow of the Rio Grande), tribal land, floodplains, and environmental habitats restrict where physical barriers can go. In the Rio Grande Valley, barriers often stand anywhere from 50 feet to a mile away from the river.