The U.S. Border Patrol is the uniformed enforcement arm of the U.S. Customs and Border Protection agency of the U.S. Citizenship and Immigration Services, in the Department of Homeland Security. Prior to 2003, it was managed by the Immigration and Naturalization Service (INS). The Border Patrol was established in 1924 primarily to control the entry of undocumented (illegal) aliens. The immediate impetus for its establishment was the dramatic influx of Mexicans, estimated at some 700,000, due to the Mexican Revolution (1910–17). Whereas almost all Mexican migrant labor had been temporary before, the revolution permanently displaced thousands who were prepared to stay in the United States. Although the 2,000-mile U.S.-Mexico border was the focal point of Border Patrol activity throughout much of the 20th century, the agency was responsible for approximately 250 ports of entry and more than 8,000 miles of land and sea borders. From the 1960s, it played an increasingly prominent role in the interception of Caribbean and Central American immigrants along the Gulf and Florida coasts. As the issue of illegal immigration became more highly politicized in the 1990s, the size and budget of the agency doubled, most directly through the Illegal Immigration Reform and Immigrant Responsibility Act (1996). With increased budgets came more sophisticated technologies, including ground sensors and infrared tracking equipment, as well as stronger permanent fences along areas of high crossing. In the 1990s, the Border Patrol made about 1.5 million arrests annually. Increased border patrols had little effect on the numbers of illegal immigrants, however, as they simply turned to more remote crossing points or paid higher prices to smugglers for riskier enterprises. In the wake of the September 11, 2001, terrorist attacks, Border Patrol duties along the U.S.- Canadian border were greatly enhanced, with additional agents and funding allotted under the USA PATRIOT ACT (2001). See also Bracero Program; Mexican immigration.