Jiu Valley is rich in historical proof of human inhabitance. The Banita fortress, a strategic outpost of Decebal, as well as other historical remnants, as the numismatic treasures discovered in the Boli cave, Jiet - Popi, and so on, date back to Dacian times. The peasants from the Jiu area (momarlanii) inherited the black and white popular costume, traditions, words and the names of mountains and rivers from their Dacian ancestors. The Romans brought new traditions and continued the exploitation of gold in the valleys, thus contributing to the enrichment of the area.

The first inhabitants of today's Petrosani are twenty serfs from Petros. They were colonized in Petrosani around 1640. The Prussian lieutenant - colonel Gotze mentioned Petrosani for the first time in a document around 1788 -1792, during his trip back form the Orient through Turkey and Romania. The text that refers to Petrosani asserts: "it is a very large village in which I saw a house built above ground."

In 1700, the map of stolnic Constantin Cantacuzino is printed in Greek at Padua. The aforementioned is the first Romanian map and it introduces the name of the river Jiu in European cartography. Jiu is also mentioned, under the name Rhabon in Ptolemy Claudius's "Geography" (90 -168). Neither the origin of the name Jiu nor Rhabon is clear to our day.

The cartographic documents of Fridrich Schwantz, printed in 1720, present the Jiu valley as covered with scattered dwellings that appeared to form a single big village. In that period existed only a few grouped abodes that formed the nuclei of villages. The aforementioned villages became the cities of today. After 1733 the Jiu valley population increased as a result of immigration.
During the 1818 census 2,550 inhabitants were registered in Petrosani alone. The predominant trade during the abovementioned time span was sheep herding. Later, in 1840, the first coal exploitations begin in Vulcan, Petrosani and Petrila. Coal mine exploatations that are owned by the Hoffman brothers and Carol Maderspach from Brasov. Industrialized development begins in 1848, and in 1857 legal formalities for coal possession rights are recognized.