It has been deeply linked for many years to the regions that constituted the counties of Urgell, Pallars and Cerdanya during the Middle Ages, with which it identifies and forms a historical and geographic unit maintained up to the present day.

In 1874 the sixty-odd towns that formed the erstwhile exempt jurisdictions of Gerri de la Sal, Mur, Montodó-Bonrepòs, the order of Saint John of Jerusalem and Meià were annexed to the diocese.

These monasteries, alongside the parochial and canonical organization (the Urgell Diocese, Solsona, Cardona, Organyà, Ponts, Ager, Mur, Tremp) would greatly influence the Christianization of the country and its human, cultural and economic development.

The canonical monasteries derived into colleges as a result of their secularization (1592), and due to their corruption, the 1851 concord eliminated them, along with the other preexisting ones (Castellbò, Guissona, Balaguer).

Mur and Àger were without a doubt the most famous Catalan canonical colleges, exempt from episcopal jurisdiction On the first decade of the Umayyad conquest of Hispania, Berber troops set up garrisons on the northernmost hilly regions and towns.

During the episcopacy of the Bishop Felix (781–799), who was accused of adoptionism by the Carolingian theologians and for this motive deposed and confined to Lyon, the city of Urgell and its church were completely destroyed by the Arabs around 793.

The territory now being free, mainly, from the Moors' power, with the help of the first Catalan Counts, they promoted the construction of a new cathedral, completed in the second part of the 9th century, to which were assigned 289 towns or villages — all the northwestern area of the Pyrenees.

At the same time, the Urgell church, ruled for more than two centuries (914–1122) by members of the Counts' families, fully entered the ring of the feudal system, which allowed it to shape for itself an extensive seigniorial patrimony, which among other cities and territories included the city of Urgell, the valleys of Andorra, the Vall de la Llosa, the Vall d'Arques and the Ribera Salada, the villages of Sanaüja, Guissona, and, from 1257 onwards, Tremp.