The area in which Petrosani is situated, was mentioned long time before it was called the Jiu Valley. Very old traces of primitive life (ceramics of potters) were found in a cave from the Straja-Lupeni hill. Later, during the Dacian-Roman wars in the first and second century after Christ, the Valley became an important strategic point in the defence of the Dacian people (the original people of Romania). More specifically, they built a fortress (fortareata) on the hills, 12 km. from Petrosani on a huge precipice. The fortress had only one access way, and represented an important point in the defence of the Orastie Mountains. It was partially destroyed during a war by the Roman emporer Marcus Ulpius Traianus and his army. The ruins of this fortress still exist, and are really worth to see!! On his way to the capital of Dacia, Sarmizegetusa, the emperor Traianus used the Vulcanului-passage in the years 105-106 after Christ. This place is situated near Petrosani and is now called the city "Vulcan". Even though the Jiu Valley is a part of Transilvania, it belonged to the Habsburgic Empire for many centuries.
Out of the chronics of Anonynius (12th century), who was the notary of the Hungarian king Bela III, we can read that the Romanians occupied these lands before the Hungarians arrived and established in the Panonic fields. It also says that the Romanian leaders Menumorut, Glad and Gelu fought a lot against the Hungarian conquest those days.
In 1462 Vulcan was mentioned for the first time in a written way.

Petrosani finds its roots in 1640, but its first written mention dates from 1788-1792.

Coal Mining started in Petrosani in the middle of the 19th century. From all around the Habsburg Empire, Polish, Czech and German workers were brought to Petrosani, to work in the coal mining. These workers mixed pretty soon with the local people.
In the eighties people were brought in Petrosani again by the communist government from all around Romania, mostly from Moldova.

Nowadays mining is the main occupation in the Jiu Valley. The mining museum "Muzeul Mineritului" in Petrosani is worth visiting to learn more about the history of mining and mining in generally.

The 4th of December is known as the Day of Saint Varvara in Petrosani. On this day the miners are not allowed to work, and they all have a day off. It is said that on this day Saint Varvara asks for sacrifices. In the past some people were even found dead, when they entered the mines on the 4th of December. Originally Saint Varvara is from Moldovia. When she was a little girl, she used to help the poor people and even gave away some of the belongings of her father. Because of this reason, he killed her.