This frontier, also called the tortilla border, is long of more than 3.000 kilometres and stretches from the Atlantic Ocean to the Pacific Ocean. The river "Rio Grande" corresponds to a major part of this frontier.
A border patrol keeps watchig on people who go to the USA and the building of a discontinue wall between the 2 countries was decided in 2006due to all the illegal traffics which existed.
Then, in spite of their variation of economic development, the USA and Mexico are both member of the NAFTA (North American Free Trade Agreement) andthat creates a lot of exchanges between these two countries. In fact, one of the main features visible on the map, is the presence of twin-cities cross-border. They are composed of an American and aMexican city. The most important are San Diego/Tijuana, El Paso/Ciudad Juarez and Laredo/New Laredo. The appearance of maquiladoras on the Mexican side supported the development of many twin-cities.These maquiladoras are factories which profit from the customs duties’ abatement to be able to produce with a lower cost of goods. American contractors settle their firm in Mexico in order to earn money.After, we can notice that there are also large regional centres such as Monterrey with 5 million inhabitants but the number of theses centres in Mexico is more restricted than in the USA. Indeed,Monterrey is one of the biggest cities of the cross-border area with Tijuana and Ciudad Juarez which have the same number of inhabitants, whereas in the USA we have Los Angeles with 16 millioninhabitants or Phoenix, Houston and San Antonio with 5 million inhabitants.
Furthermore, contrary to Mexico, in the USA, the biggest cities aren’t the twin-cities; these are metropolises somewhat far away...