After a concrete and steel border fence went up between McAllen, Texas, and Reynosa, Mexico, residents of both cities say it's been tough for people who've spent most of their lives seeing the borderlands as a single entity.

By Rachel Osier Lindley

It's just before the holidays in McAllen, a town of 130,000 on the U.S.-Mexico border. Basilisa Valdez sits in the kitchen at her sister's house, waiting for relatives to arrive. Here, that means some come from across town, and some from Reynosa, just across the river in Mexico. Before 2008, when a concrete and steel border fence went up along the Rio Grande, she says the two cities could seem like one. But after the wall, she says it's tough for people who've spent most of their lives seeing the borderlands as a single entity.

President-elect Donald Trump and border-wall proponents forget that for decades before 9/11, passage between the U.S. and Mexico was easy, especially for the towns separated by just a sliver of the Rio Grande.