A complicated process began in Añana in 1114. Its main consequence was the abandoning of the network of independent villages created between the eighth and tenth centuries and the concentration of the population in a single settlement that eventually became known as Salinas de Añana.

Valle Salado de Añana, which had belonged to various counties and boroughs over time, such as Fortaleza de Termino (Santa Gadea del Cid), was finally subjected to the power of the kings in the early twelfth century.

The solution adopted by Alfonso I of Aragon, who granted the village charter around 1114, and by Alfonso VII of Castile, who confirmed it, was to avoid direct confrontation with the major monastic institutions established in Añana. The tactic used was to respect the jurisdiction of the individuals who were under the authority of the most powerful religious centres - San Salvador de Ona, Santo Domingo de Silos in Burgos and San Millan de la Cogolla - and try to attract the rest of the inhabitants (from the villages of Añana and surrounding area) by granting privileges to those who voluntarily decided to live in the area chosen by the king to build the first royal village in the Basque Country.

After this concession, most of the residents of the six villages left their homes and settled in the area chosen by the king to build the walled town of Salinas de Añana; creating unique governing bodies at the municipal and salt works levels to control Valle Salado. This led to the creation of the Community of Knights Heirs of the Royal Salt Works of Añana, which was managed by two individuals elected on a regular basis: one represented the interests of the religious owners and the other the interests of secular owners.

The political strategy apparently paid off, leading to an increase in production and trade. However, progress was affected occasionally as it depended, to a great extent, on the power exercised by the monarch occupying the throne. If he was a weak king, the aristocracy took advantage of the situation to impose its will, even using violence, with a view to achieving maximum profitability.

A clear example of royal weakness that directly affected Salinas de Añana in certain periods was the loss of its status as Crown land in 1308, when it became the property of the monastery of Huelgas in Burgos. The situation changed again with Enrique II, who granted the Estate of Salinas de Añana to the lineage of the Sarmiento, thereafter known as the Earls of Salinas.

The town, as the rest of the territory, suffered from the conflicts among landowners in the late Middle Ages. Documents preserved from this period clearly give this impression from the thirteenth century. These conflicts prompted the council of Salinas de Añana to join the Hermandad de Castilla (Brotherhood of Castile), established in 1295, then the General Brotherhood of all the kingdoms established in 1315 and, finally, to join the Brotherhood of Alava in 1460.

Regarding commercial activities; we must note the permanent conflicts between the various salt works in Castile to control exclusive sales areas. In this struggle of interests, the Añana salt works won on several occasions, as evidenced by the privileges granted by Alfonso X in the so-called "Las Partidas" or by Sancho IV at the Court of Burgos in 1315, where Añana was granted the monopoly of selling salt in the current territory of the Basque Country and in large parts of Castilla la Vieja.