The division and re-division of Wards has much to do with the development of northern Yokohama by railroad companies. The opening of the Tōkyū Den-en-toshi Line and associated residential communities led to the rapid suburban development in this region. This was followed by the project in the 1980s and early 1990s. The core of the Kōhoku New Town became a significant commercial centre once the subway line extension between Shin-Yokohama and Azamino was completed in 1993. The influx of new population resulted in the entire “Kōhoku New Town” being re-organized into the new Tsuzuki Ward.