About two million years ago, the valley was covered by a vast natural lake with a completely different climate, flora and fauna from the current one.

As a result of tectonic movements, which generated the formation of the Apennine (defined by reliefs whose heights range from 1,200 meters of the Maddalena Mountains to 2,005 meters of Monte Sirino), the depression of the Valley was formed. With the progressive emptying of the ancient lake, (probably through the fracture of the mountain crown visible today in the remains of the Murge di S.Oronzio, at the bottom of the valley), the Agri river and its tributaries shaped the current layout of the valley.

The valley was already inhabited by the Neozoic era. In the Iron Age, the inhabitants of the valley, the Enotri, came in contact with the Greek populations. The main center of that time is located near the current Marsico Nuovo. From the second half of the fifth century. B.C. the valley is populated by small farms, due to the intensification of agricultural activities, which flank the fortified sites. This is due to a slow supremacy of Samnite people. A new ethnos takes power in this region and in the Val d’Agri: the Lucanians.

The Lucanians, in contact both with the Magno-Greek populations first, and with the Romans then, began to acquire new settlement models: an important step in this phase of "protourban" development is evidenced by the birth, between the end of the IV and the beginning of the III century BC, of the inhabited area of Grumentum where the relations between Romans and Lucanians were an alliance between elites until Grumentum became the scene of various battles including one involving Hannibal (narrated by Livio). The withdrawal of the Lucanian populations during the second Punic war was the cause of massive confiscations suffered after the end of the conflict and large areas of the valley became property of the Roman state. The more stable presence of Roman citizens in an area that has not yet been fully Romanized made it necessary for Rome to send a prefect to Grumentum. Between the Sillan and Cesarian ages, Grumentum became a colony of Rome. From this moment and especially in the Augustan and Julio-Claudian period, Grumentum, like many other centers of the Roman Empire, also experienced that period of uniformity and adhesion to the models of the Urbis by local realities. The city was equipped with a theater, an amphitheater, city walls, thermal baths, a forum with sacred and civil buildings. Grumentum was certainly one of the most important cities of Lucania for the entire imperial period and in late antiquity it became a bishopric. The Roman Val d'Agri was a particularly rich and fertile area also thanks to the exploitation of water resources evidenced by the presence of the well-preserved Roman aqueduct, which channeling the waters of some springs located downstream of the relief on which the town of Moliterno and the nearby town of Sarconi fed the urban site of Grumentum. The Roman settlements in the valley were mainly located in the plains and in the foothills with numerous farms and villas where an important production area was also located.

Grumentum managed to maintain its importance until the Greek-Gothic wars and the Langobard invasions created instability. The city was reduced and lost its role as a central pole from the fifth century, although it was established until the ninth century. The new control poles of the valley were first the small housing units located around the churches, then the Italian-Greek Basilian monasteries founded by Byzantine monks starting from 535 AD, with the Greek conquest of southern Italy. Saracen raids (872-944 AD) led to the definitive abandonment of the city and the first offshore settlements began to be structured. So between the 9th and 10th centuries Saponaria (today Grumento Nova), Viggiano, Marsico Nuovo, Moliterno, Marsicovetere were born; subsequently Montemurro, Spinoso, Sarconi and Tramutola.
In the 9th century, the division of the Langobards assigned the principality of Salerno a territory that includes all of ancient Lucania and divided into fortified castaldates due to the invasions. After the Langobards, the Normans, they found the layout of the valley with new small offshore nuclei, where they built the castles. The territory was again divided into fiefdoms between 1154 and 1168 under Federico II. The history of the South of Italy is a story of fiefdoms, a story of foreign monarchies who brought their own customs and institutions from their countries of origin. For this reason, closed communities have developed characterized by stratifications of Italic, Greek-Byzantine, Saracen, Albanian and Bulgarian cultures with strong identities linked to their rituals, their languages and agricultural, farming and woodland activities. The lack of an important urban structure in the surroundings has amplified the closure of the villages and the deep-rooted feudal structure has not allowed the development of the Municipalities as in the North. Until the unification of Italy, the valley was a territorial unit only in disasters (earthquake of 1672).

Although the communities were closed and isolated, with the feudal system a balance was created due to the specificity of the productions within the countries, so much so that between the seventeenth and eighteenth centuries the whole area experienced the moment of maximum economic splendor. It was only in 1806 that, with the Napoleonic conquest of the Kingdom of Naples, the fiefdoms were abolished. On this occasion, the French state did not bother to divide the lands taken from the fiefdoms and the clergy into small shares to be distributed to the peasants and, with the unification of Italy, the government attempted to administratively unify a territory that in fact presented cultural and economic differences. With the call to arms by the state, many men, also from the valleys, hid in the woods, marrying the cause of brigandage. Shutting down agriculture meant ditching an already poor local economy, so for the inhabitants of the valley the choice was between becoming a brigand or emigrating. Only in 1902, the Zanardelli government decided to visit Lucania but it was too late: many people had left their countries in the past 40 years due to poverty and many others would have done so in the decades to come.

Until the post-war period, the few countries remained isolated and closed. The rare and rough mountain roads make the road system complex. On the other hand, there are many non-banked forests and rivers, large uncultivated territories and the great distance between countries does not yet allow the development of large driving forces of economic and cultural life. During the Fascist twenty years, little was done, if not some reclamation. In the post-war period, with the funds from the “Cassa per il Mezzogiorno”, the “Reclamation Consortium” built the Agri barrier dam, creating the Lake of Pietra del Pertusillo (1957-1962). Subsequently (1960s-80s) the route s.s 598 Fondo Valle d’Agri, which precisely follows the course of the Agri, not considering the infrastructure between the countries, which however remain isolated. Only in the 1980s did the mountain community begin to create a supra-municipal service structure, which also includes the braces for connecting to the main road. At the same time, politics focuses services and industries on the valley floor (two poles: services are developed in Villa d'Agri and Viggiano and Grumento Nova industry, then oil), creating the economic, demographic and territorial imbalance that the whole area continues to carry around since then.