MISSION, TEXAS—About a hundred parishioners gathered for Mass at a white adobe chapel built beside the Rio Grande in 1899. Father Roy Snipes, the parish priest, tolled the rusty church bell by hand, signaling the start of a welcome-home service for migrant farmworkers and “Winter Texans”—retirees flocking back to the Rio Grande Valley for another season of warm November mornings like this. But just as Snipes began to speak, an olive-drab military helicopter—part of President Donald Trump’s troop surge at the border—drowned out his welcome message. “Grandaddy would have never believed that,” Snipes said, his white cassock billowing. “It’s like a priest saying Mass in a war zone.” The military presence only foreshadowed what might be an even starker federal presence at the chapel: La Lomita stands in the proposed path of President Trump’s border wall.

The Rio Grande Valley is the Trump administration’s top priority for new border-wall construction. The region saw 160,000 unauthorized border crossings last year, more than any other sector, though many were families turning themselves over to officials in order to seek asylum. Customs and Border Protection maps from July 2017 showed that the agency planned to build a wall segment just yards from La Lomita, which means “little hill.” At best, the plan seemed to leave the chapel on the Mexico-facing side of the wall—a liminal “no-man’s-land” south of the wall, but north of the border itself. At worst, advocates feared that the chapel could be bulldozed. Then, on February 14, Congress funded 55 miles of new walls in the Rio Grande Valley, and wrote protections for the chapel into the bill. For a moment, La Lomita seemed safe. But then President Trump declared a national emergency to unlock more wall-building money than Congress had allowed. Administration officials claimed that the congressional restrictions don’t apply to the national-emergency funds, leaving the chapel’s future again uncertain.

In November, I met the art professor and activist Scott Nicol at La Lomita. Nicol, who has been fighting the border wall since the George W. Bush–era Secure Fence Act, brought a large roll of measuring tape to see whether the chapel would fall within CBP’s planned “enforcement zone”—a 150-foot strip extending from the base of the wall, clear-cut of vegetation, featuring a gravel road, stadium lighting, and surveillance equipment. Starting at the base of the flood levee, where the wall would be built, Nicol unspooled the measuring tape, and reached the adobe structure after about 90 feet. The entire chapel falls within the enforcement zone, and its presence seemed clearly incompatible with CBP’s construction plans. In an email, a CBP spokesperson said the agency did not have plans to remove the chapel and is “working to minimize or avoid impact to sensitive areas such as La Lomita Chapel,” but declined to rule out the possibility. “That’s why we’re concerned that the chapel could be destroyed,” Nicol said.

That week, the government signed two contracts with a Galveston-based construction company to build eight miles of wall near La Lomita. Advocates ramped up their campaign to defend the chapel, nearby wildlife sanctuaries, and the private landowners who stood to lose their riverside property to the government. Valley residents have lost homes, backyards, and businesses to the no-man’s-land created by Bush- and Barack Obama–era walls. Pamela Taylor, a homeowner who has lived on the Mexico-facing side of the wall for a decade, deadpanned, “We live in a gated community.”

Fred Cavazos’s 77 acres of riverfront property has been in his family since a mid-18th-century Spanish land grant to his ancestors. Cavazos, who uses a wheelchair, rents out 30 riverfront plots for camping, fishing, and jet skiing on the Rio Grande. Three tenants are Border Patrol agents, and Father Roy Snipes docks his old motorboat there. The income, about $30,000 a year, supports Cavazos and his sister. The planned border wall would leave the property in the no-man’s-land, behind a 30-foot wall. “Who would want to lease?” Cavazos worried. “I don’t think I’ll have any tenants left.”