After the Ice Age, around 8000 BC, there were already many people living in what is today the Stockholm area, but as temperatures dropped, inhabitants moved south. Thousands of years later, as the ground thawed, the climate became tolerable and the lands became fertile, people began to migrate back to the North. At the intersection of the Baltic Sea and lake Mälaren is an archipelago site where the Old Town of Stockholm was first built from about 1000 CE by Vikings. They had a positive trade impact on the area because of the trade routes they created.
Stockholm’s location appears in Norse sagas as Agnafit, and in Heimskringla in connection with the legendary king Agne. The earliest written mention of the name Stockholm dates from 1252, by which time the mines in Bergslagen made it an important site in the iron trade. The first part of the name (stock) means log in Swedish, although it may also be connected to an old German word (Stock) meaning fortification. The second part of the name (holm) means islet and is thought to refer to the islet Helgeandsholmen in central Stockholm. According to the Eric Chronicles the city is said to have been founded by Birger Jarl to protect Sweden from sea invasions made by Karelians after the pillage of Sigtuna on Lake Mälaren in the summer of 1187.