"The United States Border Patrol (USBP) has a long and storied history as our nation's first line of defense against unauthorized migration. Today, the USBP's primary mission is to detect and prevent the entry of illegal aliens into the country, assist in the detection of possible terrorists, and interdict drug smugglers and other criminals. The Homeland Security Act of 2002 dissolved the Immigration and Naturalization Service and placed the USBP within the Department of Homeland Security (DHS). Within DHS, the USBP forms a part of the Bureau of Customs and Border Protection under the Directorate of Border and Transportation Security. In the course of discharging its duties, the USBP patrols 8,000 miles of American international borders with Mexico and Canada and the coastal waters around Florida and Puerto Rico. However, there are significant geographic, political, and immigration-related differences between the Northern border with Canada and the Southwest border with Mexico. Accordingly, the USBP deploys a different mix of personnel and resources along the two borders. Due to the fact that over 97% of unauthorized migrant apprehensions occur along the Southwest border, the USBP deploys over 90% of its agents there to deter illegal immigration. The Border Safety initiative and the Arizona Border Control initiative are both focused on the Southwest border. This report will be updated as circumstances warrant."
CRS Report for Congress, RL32562