Enthusiastic modern writers have dubbed Zacatecas ‘mother’ and ‘civiliser’ of the north of Mexico in their descriptions of the large contribution that the city made to the colonisation of the provinces of New Biscay, New León and New Mexico. Zacatecas' part in the northward expansion of Spanish colonisation, both as a base for exploration and as a source of men, was indeed great. In the following pages some account will be given of the major movements to which it contributed. The detailed history of those movements lies outside the scope of this study; but before any local study of the city is undertaken, it may conveniently be fitted into the background of colonisation over the north as a whole.

As has been seen, expansion began very soon after the settling of the primitive mining camp under La Bufa, with discoveries of ores at mines in the area of Sombrerete. But even while this was taking place, the intensity of Indian hostility was increasing. The first concerted Chichimec campaign against established settlements came in 1561; the defeat of that campaign marked the true beginning of Spanish occupation of the north, and left the way clearer than before for exploration to continue. This campaign of allied Guachichil, Zacatecos and other Indians against Sombrerete, San Martín and estancias in that area in 1561 may have received more attention that it deserves, and hence appeared more serious than it was, because of the long and eloquent report given of it by Pedro de Ahumada Sámano, the leader of the force that put it down.