Which structure currently operates as a "virtual fence:"  Boarder Wall or Mexico-United States Barrier?
Mexico–United States barrier The Mexico–United States barrier is a series of walls and fences along the Mexico–United States border aimed at preventing illegal crossings from Mexico into the United States. The barrier is not one continuous structure, but a grouping of relatively short physical walls, secured in between with a "virtual fence" which includes a system of sensors and cameras monitored by the United States Border Patrol. As of January 2009, U.S. Customs and Border Protection reported that it had more than 580 mi of barriers in place. The total length of the continental border is 1,989 mi .
Amistad Dam Port of Entry The Amistad Dam Port of Entry is a port of entry into the United States from Mexico. It was built when Amistad Dam was completed in 1969. The Dam was a bi-national effort to establish flood control on the Rio Grande and provide sources of water. Although US Department of Transportation statistics combine traffic counts with Del Rio Texas Port of Entry, approximately 65,000 vehicles crossed the dam into the US in 2005.