The area west of Shinjuku Station was historically known as Yodobashi, on an elevated plateau separating the High City [Yamanote] land from Tokyo’s Low City [Shitamachi]. The area first came into prominence as one of the stations along the Koshu-Kaido, one of the five major highways of the feudal period. It remained largely rural on into the Taisho Era (1912-1926), until after the 1923 Great Kanto earthquake.
In 1898, the Yodobashi Water Purification Plant was opened in Shinjuku, Japan’s first modern waste water treatment works. It would be shut down in 1968; replaced with Tokyo’s largest concentration of skyscrapers, including the Keio Plaza Hotel and the Tokyo Metropolitan Government buildings.