Nykvarn was its own municipality under the name Turinge, but with the municipal reforms in the 20th century, Nykvarn became part of Södertälje.
In 1995, several organizations carried out a survey investigating interest and the possibility of building a new municipality, then the Chamber of Deputies carried out a similar investigation at the request of Södertälje Municipality. In 1997, the investigation is complete, and shows that there is both interest and financial opportunity for Nykvarn to become its own municipality.
A referendum is held in March 1997, where participation is around 70 percent, and 77.2 percent of the votes say yes to partition. The government approves the division and Nykvarn officially becomes its own municipality on January 1, 1999. During 1998, Nykvarn is formally governed by the municipal division committee, while five division delegates, including Christina Berlin, lead the work to build the new municipality.