Pancho Villa, prostitutes and spies: The U.S.-Mexico border wall's wild origin story

On an August afternoon in 1918, a mysterious man approached the U.S.-Mexico border in the bustling town of Nogales.

For decades, the boundary between the two countries had been little more than an imaginary line in the sand, marked only by the occasional - often crumbling - pillar in the Sonoran desert. But rampant smuggling, the Mexican Revolution and the outbreak of World War I had split the border town in two, sowing fear and stoking tensions.

As the man walked towards Mexico, where Mexican soldiers were waving him on, a U.S. Customs inspector suddenly ordered him to halt.

Unheeded and suspecting the man was a smuggler, the customs inspector drew his gun.

https://www.sandiegouniontribune.com/news/nation-world/ct-mexico-border-wall-history-20190110-story.html