Why Spain able to establish firm control over northern Mexico?

Spain was never able to establish firm control over northern Mexico. The region was largely under the control of indigenous peoples until the mid-16th century, when the Spanish began to establish a presence in the area. However, even then, the Spanish control was tenuous, and the region was frequently plagued by indigenous uprisings. It was not until the end of the 18th century that the Spanish were able to fully pacify the region.