Södertälje ( , ) is a city in Södermanland and Stockholm County, Sweden and seat of Södertälje Municipality. As of 2017, it has 72,704 inhabitants. Södertälje is located at Mälarens confluence in to the Baltic Sea through the lock in the Södertälje Canal. Since year 2000, it is the largest city located entirely within the province of Södermanland. History Ancient history It is estimated that the first people reached the area around what is today Södertälje during the Stone Age, about 4000 BC. They formed settlements around 3000 BC, when the peasant culture is believed to have reached the area. Around 1500 to 400 BC, the strait between Lake Mälaren and the Baltic Sea narrowed due to the post-glacial rebound. Thereafter boats had to be towed over the sand ridge, which created job opportunities. Trade and service emerged. Ansgar passed through Södertälje on his voyages to Birka in his efforts to Christianize Sweden in 829. Södertälje was first mentioned in historical sources in 1070, when Adam of Bremen mentioned the town in a description of the road between Skara and Birka in his work . However, the area was inhabited long before then. Södertälje received city privileges in the 1300s. The castle Telge Hus was built at Slottsholmen during the 1300s. From here, Telgehus county was administered between the years 1318 and 1527. The county included Öknebo, Hölebo and parts of Svartlösa districts. Archaeological excavations have shown that the castle was surrounded by a moat. It is still partially visible on Slottsholmen's northwestern shore. Originally, the city was simply called Tälje (several spellings are known; including Telge, Talje, and Tælga). In 1622, the prefix 'south' was added to distinguish from the then recently founded town of Norrtälje, located 110 km northeast of the city. Statistics Sweden started using the modern spelling in 1900. The city first used St. Olof in its coat of arms. At the beginning of the 17th century, he was replaced by Ragnhild of Tälje (). After her pilgrimages to Rome and Jerusalem, her relics are said to have been buried in Södertälje. Duke Charles (subsequently became King Charles) actively invested in Södertälje as a commercial and maritime city during his time as Duke of Södermanland, which contributed to growth. A port was built just south of the city. It was not until the 1740s that the city began with industrial manufacturing in addition to shipping and