Mexico–United States border wall

A border wall has been built along portions of the Mexico–United States border in an attempt to reduce illegal immigration to the United States from Mexico. The barrier is not a continuous structure but a series of obstructions variously classified as "fences" or "walls".

Between the physical barriers, security is provided by a "virtual fence" of sensors, cameras, and other surveillance equipment used to dispatch United States Border Patrol agents to suspected migrant crossings. In May 2011, the Department of Homeland Security (DHS) said it had 649 miles (1,044 km) of barriers in place. A total of 438 miles (705 km) of new primary barriers were built during Donald Trump's first presidency, dubbed the "Trump wall", though President Trump had repeatedly promised a "giant wall" spanning the entire border and that Mexico would "pay for the wall," neither of which were done. The national border's length is 1,954 miles (3,145 km), of which 1,255 miles (2,020 km) is the Rio Grande and 699 miles (1,125 km) is on land.

President Joe Biden signed an executive order on his first day of office, January 20, 2021, which ordered a pause in all construction of the border wall no later than January 27, 2021. By December 2021, many contracts had been cancelled. On July 28, 2022, the Biden administration announced it would fill four wide border wall gaps in Arizona near Yuma, an area with some of the busiest corridors for illegal crossings. In October 2023, President Biden announced that he was restarting border wall construction on some parts of the border due to the surge of migrant crossings, constructing an additional 20 miles (32 km) of border wall.

In January 2025, re-elected president Donald Trump pledged to finish the border wall during his second term. In a February 10, 2026 interview, Department of Homeland Security (DHS) Secretary Kristi Noem stated that DHS is on track to complete border wall construction by January 2028.