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 .
Boundary Treaty of 1970 The 1970 Boundary Treaty between the United States and Mexico settled all then pending boundary disputes and uncertainties related to the Rio Grande (Río Bravo del Norte) border. The most significant dispute remaining after the Chamizal Settlement in 1963 involved the location of the boundary in the area of Presidio, Texas, and Ojinaga, Chihuahua. The river channel was jointly relocated to approximate conditions existing prior to the dispute which arose from changes in the course of the river in 1907. The International Boundary and Water Commission was charged with its implementation. The American-Mexican Treaty Act of October 25, 1972 authorized the United States Section's participation. The project was undertaken in 1975 and completed in 1977.