Hi Ishbel!
I have a map over Norrkoping from 1769. The area north of the river was long ago called nordan til, to the north,or Nya staden, the new town.
In the old days, the town was mainly on the south side of the river.
1572 a plan was made for the north side , but only a few houses were built before 1614, when the town started groving.
I am not sure of Stora gatan, main street, but it is probably Kungsgatan.
In old times the only bridge over the river was at the south end of Västgötagatan that led, up hill, to Kungsgatan, and the main road to Stockholm and central Sweden.
Best Wishes
Åke Bjurström Norrköping