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 .
Chateaugay–Herdman Border Crossing The Chateaugay–Herdman Border Crossing connects the towns of Hinchinbrooke, Quebec to Chateaugay, New York on the Canada–US border. The crossing can be reached by New York State Route 374 on the American side, while Chemin Herdman connects it to Quebec Route 202 on the Canadian side. This crossing is open 24 Hours per day, 365 days per year. Border inspections at the crossing were established in 1933 in response to a surge in alcohol smuggling from Canada into the United States. The U.S. border station and inspector's residence built at that time are still in use, and were listed on the National Register of Historic Places in 2014.