Cada territorialidad está marcada por una frontera. Durante el siglo XIX, los límites territoriales fueron modificados tanto en el norte como en el sur; sin embargo, la frontera no sólo es un límite legal y natural que se negocia en comisiones internacionales y tratados. En México existe una pugna interna entre dos grupos para proteger la frontera de sus territorios. Este siglo estuvo caracterizado por la mobilidad de la población, además de cambios importantes tanto en la división politica como en la propiedad territorial. Algo importante que hay que resaltar de este trabajo es que el  concepto frontera será interpretado de muchas maneras, dependiendo de los valores e intereses.Every territoriality is drawn by a border. During the XIX century, the country limits were modified such as the north and the south. But a territo¡ial frontier is not only the legal and natural limits which are negociated by international commissions and treatises. Inside Mexico, there is a persistent fight between different groups, to protect the "border" of their lands. This is a century basicaly characterized by population mobility and also by important changes, as much in the political division as in the land property. The frontier concept will be interpreted in many ways, related with the values and the defend of different kind of interests Mexico modifies it's internal and international frontiers, and finally, will be amputated and distributed according to the XIX century modernizing ideas. This teritoriality is for the present Mexicans, one of the most important legacies.