A lot gets said about "America's porous borders," especially in an election year. Forget for a moment, about the argument about whether or not a wall would be effective along the U.S.-Mexican border (and forget about who is going to pay for it). Right now, there is no wall and there are three borders, guarded by a thin green line called the U.S. Border Patrol.
The boats, horses, and men of the Border Patrol weren't originally meant to be on guard against illegal Mexican immigrants, drugs, and guns from coming over the southern U.S. border, they were formed to keep the American southwest free of illegal Chinese immigrants.
The Border Patrol is no joke. The agency has a Congressionally-mandated 21,370 agents covering a staggering 19,000 miles across the U.S. northern and southern borders as well as the Caribbean. It has its own SWAT team, special operators, and search and rescue squads. They finish a 13- to 21-week long basic training course (depending on how well the trainee speaks Spanish) and then complete 12 to 16 weeks of field training at their first duty station – just to call themselves "agent."
In 1904, the nascent Border Patrol was known as the Mounted Guards. Operating out of El Paso, Texas, 75 horsemen scanned as far west as California in an attempt to stem the tide of Chinese immigration.
Around the turn of the 20th Century, Congress passed the Chinese Exclusion Act, restricting immigration from China. During the Gold Rush and the building of the Transcontinental Railroads, Chinese laborers were welcomed to the U.S. in droves. After the economic booms of the post-Civil War years and the end of the Gold Rush, the once-welcomed source of cheap labor lost their appeal and public opinion quickly turned sour.
A mix of these Mounted Guards, U.S. troops, and Texas Rangers kept an eye out for the unwanted immigrants. In 1915, the Mounted Guards became Mounted Inspectors and had Congressional authority – but they had to bring their own horses.
In those days, catching customs violations were more important than cutting off illegal immigration. The Border Patrol as we know it was born in 1924, both as a response to Prohibition and to Congressional restrictions on the number of legal immigrants coming into the U.S.
With Prohibition, defending the northern border became as important as the south. Based in Detroit, the northern area had to cut illegal immigration as well as the illegal import of Canadian Whiskey. The American government authorized 450 agents to patrol all of America's borders.
In 1925, Pancho Villa and his "Villistas" invaded American territory, sacking Columbus, New Mexico and killing it inhabitants. It was the largest American loss of life on American soil until the terror attacks of September 11, 2001.
Columbus didn't receive Border Patrol agents until 1927 – two men guarding 135 miles of border, a microcosm of the modern Border Patrol's modern long-distance mission.