Hrastnik's story begins somewhere at the beginning of the 1st millennium. A discovery made in the 1990’s shows that boatmen used to pass this area in the period between 1st and 4th century. The Sava river was known to be very dangerous and unpredictable, and for that reason people built a sanctuary on its shores. There, they used to pray for or thank for a safe passage. The river was the first main path used mostly for carrying cargo. The valleys surrounding the river were already populated, but people mostly engaged in agriculture – a key pillar of their survival. Coal has played a large part in the development of Hrastnik. Realizing that it burns better than wood (with the latter also taking a lot of time to renew itself), the local coal mine was bought by a bigger coal company from Trieste. They managed to increase production and to create an industrial railway. Due to the proximity to the better energy source, two factories also moved to this valley. In 1859, the Trieste tin factory moved to Hrastnik where the chemical factory was established as its successor. A year later the glass factory from Jurklošter arrived to its fourth and final destination. They both started operating in 1860 and continue to produce new products even to this day. The three industries provided a secure base for the town’s development. The year 1849 saw an even an earlier breakthrough for the valley. The miner’s band played to welcome the first train arriving on the newly built part of the historic Austrian Southern Railway. The railway allowed for further development due to better connections. The town was first a part of the old Trbovlje municipality, while Dol formed one if its own. In 1934, Hrastnik became a part of the Dol municipality and later turned independent in 1955.