The banks of the Rio Grande bristle with concertina wire. At intervals, Texas National Guardsmen and other troops sent by President Trump stand guard over the border.

And several times a week, the sheriff of Maverick County, Texas, drives back and forth over an international bridge — to do his dry cleaning.

“I get my hair cut in Mexico too,” the sheriff, Tom Schmerber, said during a recent trip as he hauled a garbage bag filled with his dirty uniforms.

Those chores are the kinds of routine, international economic transactions that people on the border have long taken for granted — and that people far from the border, especially those making policy in Washington, D.C., rarely consider.

And they are threatened by tightening controls that are already hampering crossings for many would-be consumers, investors and business interests in Mexico and the United States. Formerly bustling downtowns near border crossings have been transformed by successive clampdowns. Fewer shoppers mean many vacant storefronts.

And now, President Trump has injected still more uncertainty into border communities. Rounds of deportations, military deployments and especially the looming worry of punishing tariffs on Mexican goods threaten to upend the economic life of already fragile border cities.