This month, the president tweeted again: “The Fake News Media keeps saying we haven’t built any NEW WALL,” he wrote, apparently in reference to the barrier in Calexico. “Below is a section just completed on the Border. Anti-climbing feature included. Very high, strong and beautiful! Also, many miles already renovated and in service!”

Amid a continuing national debate about the border, which has resulted in the longest government shutdown in history, many in this town of 40,000 have struggled to reconcile ominous warnings they see projected from the White House about life on the border with their own experiences living in the quiet agricultural community 120 miles east of San Diego.

Calexico has long celebrated its interdependent relationship with Mexicali, its sister city directly across the line; the two cities’ downtowns are bisected by pillars where the border lies. Shoppers from urban Mexicali, which has a population of about 1 million, are vital to Calexico’s small-town economy and cross to shop at large outlet stores on the American side. Americans head to the Mexican side on weekends for cheap health care, entertainment and concerts.

“We’re right up against each other. Each city depends on the other,” said Hildy Carrillo, the executive director of the Calexico Chamber of Commerce, who like Ms. Hurtado did not vote for Mr. Trump. “The families are on both sides of the border. The businesses are on both sides of the border. And the education, the entertainment and the culture are on both sides of the border. Punto.”

[Read about how charities are stepping in to help released migrants.]

Rather than a border wall, residents here express enthusiasm for modernizing the Calexico West Port of Entry, which they hope will expedite traffic and allow for a fluid flow of business between the two sides. The number of legal northbound crossers each day, leading to hourslong lines, is astounding: about 20,000 pedestrians and up to 20,000 vehicles, according to the General Services Administration.