Nowshahr is part of kojur area and kojur is part of Ruyan.

Ruyan is a land in the west of Mazandaran Province, Iran.
This land includes Kojur, Kalārestāq and Tonekabon.

The city of Kojur was the centre of the land of the Ruyans.
Ruyan has always been part of the Tabaristan, nowadays called Mazandaran province.
The Ruyan was also called the Rostamdār, Ostandār and Rostamdele.
Nowshahr is part of kojur area and kojur is part of Ruyan. 
Ruyan is a land in the west of Mazandaran Province, Iran. This land includes Kojur, Kalārestāq and Tonekabon. 
The city of Kojur was the centre of the land of the Ruyans. Ruyan has always been part of the Tabaristan, nowadays called Mazandaran province. The Ruyan was also called the Rostamdār, Ostandār and Rostamdele.
Nowshahr