The history of the border between Mexico and the United States extends alongside 200 years and 2,000 miles - the tortuous epic of a man-made line that has not only hardened and become more solid over time, but has changed meanings too. In the beginning, it was an idea - the approximate and inhospitable edge of the vast Spanish Empire and the beginning of no man's land. Then, it was a line on paper - a porous boundary with no physical barriers. In times of peace, it was a place of trade and cooperation; in times of conflict, it was the point where two different peoples clashed, as well as the meeting of the North and South of international geopolitics.

Two centuries ago, the border was formed by vast deserts and dangerous regions in which nobody wanted to live - a vaguely defined and surveyed boundary. Today, in the second decade of the 21st century, despite being located in one of the most inclement habitats in the world, it is also the world's busiest. It functions like a country in itself considering the volume of economic operations carried out across the line, not to mention being one of the most monitored regions of the planet. Some experts have even called it a low-warfare zone. Consider, for comparison's sake, the border between Belgium and the Netherlands, where crossing means going from one pub to another, and it is hardly realized when one leaves one nation or the other. Or consider the open limits of Poland and Ukraine, which consists of beautiful green pastures decorated with all kinds of art.

How did the border of Mexico and the United States transition from a wilderness to an overpopulated, violent, dynamic, buoyant, culturally dynamic land in such a relatively short time, where a plethora of legal and illegal goods cross in both directions? Curiously, there was a time when the two countries were not even neighbors. France was between them, possessing the vast land of the Louisiana territory, where Napoleon wanted to establish a French empire in the Americas. At that time, Mexico had the official but artificial name of "New Spain" - misleading, since atlases from the 16th century had already named it "America Mexicana" - and the United States was approximately the size of the present-day United Kingdom and Ireland combined. The disturbances in Europe soon put the two most conspicuous countries of the continent side by side, and these two North American nations garnered the world's attention in the 19th century.

Certainly not everything has been bad in the relationship between the two nations. In fact, the border has developed its own traditions, history, and personality into one not entirely Mexican or entirely American. Timothy Brown, a scholar of the frontier and globalization, correctly points out that "to most Mexicans, their northern states, with half their nation's land but only one-fifth its people, seem too American, a bit alien, vaguely un-Mexican," and likewise, "to many Americans, their own Southwest sometimes seems similarly alien and terribly Hispanic." Thus, on numerous occasions, both countries have found along the line a way of helping each other for mutual benefit. By promoting the colonization of the far north from the late 19th to the early 20th century, President Porfirio Díaz helped the southern United States develop a thriving agricultural economy sustained by a Mexican labor force.