For decades, there was no physical barrier between U.S. and Mexico, until this battle

There was no physical barrier between the U.S. and Mexico for decades -- until one critical battle at the border changed it all.
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The Battle Between the US and Mexico that Brought a Permanent Fence to the Southern Border

It was late afternoon on a blazing August day in 1918. Zeferino Gil Lamadrid was on his way home from doing some business on the Arizona side of the Nogales, a city that straddles the border between ...