Immigration and border security has become a frontline in US politics and a key battleground in the race for the White House.
 
So, big stakes on the political front, but also big money, and big questions, with the same private contractors from Iraq now involved in building a high-tech fortress America.  
 
This week Inside USA travels to the US-Mexico border to look at how big business is positioning itself to tap into the lucrative border security market.
 
One of the first to get there was Boeing - America's second largest defence contractor - with Project 28, a so-called 'virtual fence' to police 28 miles of border near Tuscon, Arizona - a high traffic area for migrants.

And another name is present too. Blackwater - without doubt the most controversial private contractor in Iraq.

The company has started to manufacture surveillance blimps - clearly aimed at the border market.

Last year Blackwater announced plans for an 824 acre training facility just eight miles from the US-Mexico border.

The local community protested, and Blackwater last week said that it was dropping its plans to build the training camp.

This episode of Inside USA aired from Saturday, March 15, 2008.