Since the terrorist attacks of September 11, 2001, the focus of the Border Patrol has changed to detection, apprehension and/or deterrence of terrorists and terrorist weapons. Although the Border Patrol has changed dramatically since its inception in 1924, its overall mission remains unchanged: to detect and prevent the illegal entry of aliens into the United States. Together with other law enforcement officers, the Border Patrol helps maintain borders that work, facilitating the flow of legal immigration and goods while preventing the illegal trafficking of people and contraband.
The Border Patrol is specifically responsible for patrolling the 6,000 miles of Mexican and Canadian international land borders and 2,000 miles of coastal waters surrounding the Florida Peninsula and the island of Puerto Rico. Agents work around the clock on assignments, in all types of terrain and weather conditions. Agents also work in many isolated communities throughout the U.S.
One of the most important activities of a Border Patrol agent is line watch. This involves the detection, prevention and apprehension of terrorists, undocumented aliens and smugglers of aliens at or near the land border by maintaining surveillance from a covert position, following up leads, responding to electronic sensor television systems, aircraft sightings, and interpreting and following tracks, marks and other physical evidence. Some of the major activities are traffic check, traffic observation, city patrol, transportation check, administrative, intelligence, and anti-smuggling activities.