After the Catalan conquest in 1235, King James I of Aragon, the Conqueror, granted the town of Eivissa a Chart of Franchises stating the rights and privileges of the inhabitants of the Pitiusas Islands. One of the most significant privileges was the concession, in 1299, of a municipal system of organisation, a local government institution that was named the Universitat.
The islands of Eivissa and Formentera were thus organised as a single municipality with their capital in the town of Eivissa. As an autonomous governing body, the Universitat could take decisions in most matters, dividing itself into various strata or classes: the upper class (noble knights and society’s upper class), the middle class (sailors, merchants and artisans) and the outsider class (people from the countryside, the rural dwellers). In 1454, an election system was granted for the various posts (for both jurors and officials), bearing the name sach i sort (sack and luck). This system involved placing the names of applicants for the different positions in a bag. A child under 7 years of age had the task of drawing the names of those people who would serve as jurors or officials for a specific term.
The 'Decreto de Nueva Planta' (Comprehensive Reform Decree), issued by King Philip V in 1715, abolished the Universitat and replaced it with the Town Council, although there was no definitive change in the structure of this body until 1724. From then on, the jurors were known as regidors (town councillors) and were appointed by the Royal Court of Mallorca at the suggestion of the governor of Eivissa.
In 1782, Spanish King Charles III granted the town of Eivissa the title of City, which was an essential requirement for Eivissa to have its own bishopric. That same year, Pope Pius VI authorised the creation of the Bishopric of Eivissa.
The Universitat building was located in the Cathedral Square, and the city authorities also resided on these premises. Today this building also houses the Archaeological Museum. When the Dominican monks of the Monastery shut themselves away from the world in 1835, the building was vacated and later came to house various institutions, one of which was the Eivissa City Council, which would be relocated in 1838. A short time later, other buildings of the former Monastery (built during the 16th and 17th centuries) were occupied by the municipal hospital, the prison and the Colegio de Segunda Enseñanza (Secondary School). The Eivissa City Council currently occupies the entire area of the non-religious part of the Monastery building.
Although the Eivissa City Council was the local government institution of the two Pitiusas Islands up until the 1830s, the structure was modified, allowing other municipalities to be permanently established in 1837 with the addition of 5 new town councils that are very much alive today. This organisational structure changed in 1870, when the Municipal Council of Formentera merged with that of Eivissa, a union that would last until 1888. The lack of both political and economic benefits led the people of Formentera to once again demand their separation from Eivissa to form their own independent Municipal Council.
The municipality of Eivissa, with a surface area of less than 11 square kilometres, is the smallest on the Pitiusas Islands and the second smallest on the Balearic Islands.