Claudine LoMonaco, border correspondent for Arizona Public Radio, takes a trip along the US - Mexico border to examine how life and culture is changing as America constructs fortified walls, wire fences and watchtowers to prevent illegal infiltration.
She describes how the famous twinned border towns of El Paso/Ciudad Juarez, Nogales Arizona/Nogales Sonora, San Diego/Tijuana have been changed by the militarisation of the border.
Once a romantic and sleepy backwater, the border is now regarded by many as a low-grade war zone and the most dangerous frontier on earth, as drugs and people are smuggled north and guns move south.
It runs from the Gulf of Mexico to the Pacific Ocean - through some of the most remote and dangerous terrain in the world - and has been the setting for the world's biggest modern migration.
Some 12 million Mexican-born people now live in America, many of them illegally, and the number is set to rise significantly.
She travels with the border patrol in search of the traditional desert crossings.
The programme observes the wall in its fully-fortified might as it divides the cities of Tijuana and San Diego, and finds it again in the middle of an Indian Reservation, cutting the traditional desert tribal lands in half.
What role has this border played in the American imagination and how does it play out in the cultures on both sides?
Claudine judges how well the new wall has worked in keeping check on the drug traffic and she reports on how this multi-million dollar divide has changed the habits and fortunes of the illegal migrants.
Why do so many continue to die in agony and desperation in the American wilderness?