Södertälje also has a fantastic history that stretches from the 8th century to modern times. An archaeological survey shows that Ansgar, the Apostle of the Nordic Region, passed Tälje on his way to Birka year 829. Since then, a lot has happened in Södertälje, perhaps mostly because of its situation between the Baltic Sea and Lake Mälaren. Among other things, a castle was built in the late 14th century just north of Tälje to protect the city and make tax recovery more efficient. Archaeological excavations show that it was surrounded by a moat and a bag lock. The castle was named Täljehus, and it can be visited as an ancient monument.

By the mid-1850s, the government decided that Sweden would finally have a rail network. As a result, västra stambanan, between Stockholm and Gothenburg, was built, which is still in use today. The western main line was inaugurated in 1862 and meant that Södertälje got a railway connection to Stockholm. The opening of the rail between Stockholm and Södertälje took place on October 24, 1860 and since then Södertälje has had daily relations with the Swedish capital.

Södertälje is also a significant industrial city with 19,000 daily commuters to the city. Södertälje accounts for as many as 20 percent of Sweden's net trade as two of the largest companies based in Södertälje are Astra Zeneca and Scania.