In 1564, King Felipe II took control of all the salt works in the kingdom by means of the so-called "Monopolio de la Sal" (Salt Monopoly). Although he honoured the ancient privileges and the Community of Heirs of Añana preserved their rights of ownership, they were forced to surrender the entire production to the new royal warehouses and to work under strict rules established by the king's officials who settled in the Valley.

The Royal Officials and the workers had been aware, since at least the sixteenth century, that the Añana salt works could produce much more than it was producing, and that this shortfall was due, in a large part, to the poor infrastructures of the previous phase. Therefore, in 1801, the royal authorities, headed by the Architect General of Royal Revenue, Juan Manuel de Ballina, forced the owners to overhaul Valle Salado completely with a view to improving the quality of the salt and increasing production by changing the production system.

During the nineteenth century, after the French invasion, which delayed the project, we can detect a significant change in the ownership regime of the valley. We are referring to the confiscation of church property that took place in Añana in August 1843 and that led to many salt farms - recently renovated by churches and monasteries - changing hands and being taken over, through purchase transactions after a previous phase of speculation, by former employees. This resulted in the fragmentation of the ownership in the valley.

Finally, we must mention, as one of the key events in the history of the valley, the repercussions of the overthrow of Isabel II in 1868 and the 1869 Constitution, of a liberal nature. That year, the Mining Act was passed, leading to the sale of all the state-owned salt works and putting an end to the salt monopoly.

The main consequences of the new law were the cancellation of the comfortable contract for 30,000 bushels that the Añana salt workers had with the state and the liberalisation of the sector regarding production and marketing. Although this measure was not well received at first, the competition actually led to the maximum expansion period of the salt works.

Due to the far-reaching reforms introduced in the early nineteenth century, Valle Salado enjoyed great advantages over its competitors because it greatly increased production and managed to produce high-quality white salt that was put on display at the universal exhibitions in London (1851 and 1862), Paris (1855, 1867, 1878 and 1889) and Philadelphia (1876). Consequently, the Añana salt works was a financially profitable business until the mid-twentieth century.