Around 1245 Frederick II, who in 1240 had founded the town of Fregellae, near Ceprano, at the other main entrance of the Kingdom, decided to found the city of Aquila in defense of what he considered the most threatened mountain pass of the kingdom. That same year the King issued a "diploma" ordering to build a "unius corporis civitas" among the many " terrae velut in membra dispersa " in the middle of the two "castra" of Forcona and Amiterno, that is to say at a narrow junction where the four valleys merged.
The new city was to be populated with a percentage of people coming from the several dozen "terrae" scattered in the territory between Montereale and Corno (to the north and west) and San Benedetto in Perillis and Beffi (to the south and north). The diploma considered the entire area a "civitas" and the new town is a direct projection of the "terrae" around. The city was to have walls, two yearly market fairs lasting twenty days were to be held, and three small markets each week. In each of the four quarters of the would-be city an area was assigned to each of the communities of the four valleys of origin, where they would build their homes and church.
The quarter of Santa Maria would house the inhabitants of the Ansidonia valley, San Giorgio the inhabitants of the central Aterno valley, San Pietro the villages of the Amiterno valley and San Giovanni the valley of Tornimparte, each village having its own land inside its quarter. The new "universates" were given the property of all the woods and forests of the villages that were being united, as well as the territory of the former village of Aquila and nearby areas that would be covered by the new city.
And the city of Aquila was also given the power to grant lands (for sale, for rent and for free) to new tenants, including those coming from outside the county of L'Aquila, that may want to move there. Finally, the inhabitants of the territory were declared free from all feudal subjection, and the territory would be directly under the Royal Jurisdiction "tamquam specialem cameram".
The castles of the county - except for some royal castles - ought to be destroyed after two months of the opening the new city, and never restored in the future. The feudal lords who lost their rights should have been compensated by their vassals for "one-off" one-eighth of their property, but making sure that they would have lands in no more than three or four places in the territory. The diploma concluded with an order to build a royal castle at the expense of the villages within the city.
25 years later we learn from a bull of Pope Alexander IV that the city had been built and that, in 1257 the bishopric of Forcona was moved to Aquila. Not all transfers had already taken place, however, since in some lands, as Barile, Ocre and Fossa, the barons, very powerful at the court of Frederick II, hindered the transfer of populations, and this immigration took place later, when after the fall of the Swabians, the resistance of the barons ceased.
Other lands that were farther away - San Benedetto, Collepietro, Navelli, Civitaretenga, Bominaco, Caporciano, Bussi and San Pio) did not feel the attraction of the new city; some of them, subject to the spiritual jurisdiction of the Monasteries of San Benedetto and Bominaco, preferred not to move under a different authority. Consequently, the larger original urban areas where each village had its own building sector and that also included the hill of Collemaggio, was reduced to the territory contained within the new walls of 1316. Individual immigrants from eastern communities (of the diocese of Valva) did not have their sector, but lived scattered in other quarters and came to worship in the churches of other communities.
The first data on the population of the county of Aquila go back to 1269. From the total taxes (563 ounces of gold) levied according to the "ratio focularia" - that is a head tax on each head of family which might be 30 grana the number of "fuochi" could be 11,260, and therefore about 56,300 inhabitants. But there is no way to know how many lived in Aquila and how many in the original villages.
The growth of the city was soon interrupted by the fire that Manfredi ordered to destroy the city; in 1294 it is described as "non plenam civibus urbem, sed ob spartiis certis signatam spemque futuram". In the following century the territory of Aquila expanded, the castle of Machilone to the western border joined the city in 1302; soon after the inhabitants of the villae of Borbona, Laculo, Villa Sigillo, Latonerio, Pretepede, Machiloni, Foro, Faiscolo, Santonia, Vacunio, asked King Charles II to be united in one community called La Posta, which then became part of Aquila.
A century later the situation was not very different: in a diploma of Giovanna in 1364 it is stated that, since the quota between the urbanized population and those scattered in the countryside was 1 to 10, and the latter were helpless against raids, the countryside communities were authorized to build "fortellitiae" where they could find shelter.
Two of these forts were south of Aquila and others were in the north. These fortresses were to be approved by the Universitas of Aquila and host its "officiales"; construction and wages for the garrison were borne by the villages. In the same year 1364 another document of Queen Giovanna, acknowledging that the city was greatly depopulated "propter binam jam mortalitatis cladem et epidemie pestem," ordered that all inhabitants of the county, if they were strong or wealthy, were to move with their families to the city. From the verse Chronicle by Buccio di Ranallo we learn that in 1375 the city had about 3000 fuochi (14,000 inhabitants) and the county other 12,000 fuochi (approximately 56,000 inhabitants).
Other misfortunes came with the war for the supremacy of Ladislaw, during which the castles of Porcinaro, Rascina, Vio, Vigliano, Vasto, San Pietro, Jenga, Corno, Rocca di Corno, Piscignola, Rocca delle Vene and Pedicino were ruined and "incolis derelicti".
In the early 15th century there is an onciario which provides the number of fuochi at that time subdivided in all the villae of the county, including Machilone, La Posta, S. Ogna, Antrodoco and Borbona, that had been added to the original foundation. Unfortunately, this census made no distinction between the urbanized inhabitants and those that were living in the villages. The fuochi were 3867 and therefore the residents to about 20,000, which confirms the serious damage caused by war and the 1347 epidemic. Among them the most populous lands (ie those with over 500 fuochi) were Paganica, Barisciano di sopra, Bazzano, Bagno, Rocca di Mezzo, S. Vittorino, Pretoro, Pizzoli, Rodio, Lucoli and Tornimparte.
In 1421 also Antrodoco with its fortress became part of the county and in 1451 Farindola and Monte Bello. With their annexations to Aquila, these villages acquired the right to a sector within the city and other benefits of citizenship. In the mid-15th century Aquila had greatly consolidated its institutions, with a mint, a law court for first, second instance and appeal, it was governed by five men called "I cinque delle Arti" and had been granted fiscal and judicial privileges.
In 1458 a "Studium" was established for lectures in sciences and in 1447 an "Ospedale Maggiore" which merged all the hospitals of the city and the county. Historian Pandolfo Collenuccio (Pesaro, 1444 -1504) called Aquila "potentissima città del Regno " and writer Giovanni Pontano (1426, Cerreto di Spoleto-1503, Naples) said it was "civibus auctoritate et opibus clara, regionisque totius caput" adding that the people, though devoted to sheep farming and the textile industry, were expert in war and feared by their neighbours.
Aquila continued to grow in importance, and Neapolitan historian Camillo Porzio (Napoli, 1525 -1580) stated that in 1480, "from the ruins of nearby places (the city) was so increased, that for men, weapons and wealth was reputed first after Naples" and added that, having the Camponeschi family established almost a principality, people lived "almost as in an independent republic."
However, in the meanwhile the vital exchange between city and countryside had started to decrease. In 1478 as a result of a serious plague in which killed about 20,000 people, for fear of contagion and a disagreement on the allocation of taxes between "citizens" and "farmers", many countryside communities under local mayors began to separate from the city. Then, In the course of the following century the occupation of the Spaniards marked the beginning of the decadence.