In 1634, during the Edo period, as the outer moat of the Edo Castle was built, a number of temples and shrines moved to the Yotsuya area on the western edge of Shinjuku. In 1698, Nait?-Shinjuku had developed as a new (shin) station (shuku or juku) on the K?sh? Kaid?, one of the major highways of that era. Nait? was the family name of a daimyo whose mansion stood in the area; his land is now a public park, the Shinjuku Gyoen.
In 1920, the town of Nait?-Shinjuku that comprised large parts of present-day Shinjuku, parts of Nishi-Shinjuku and Kabukich? was integrated into Tokyo City. Shinjuku began to develop into its current form after the Great Kant? earthquake in 1923, since the seismically stable area largely escaped the devastation. Consequently, West Shinjuku is one of the few areas in Tokyo with many skyscrapers.
The Tokyo air raids from May to August 1945 destroyed almost 90% of the buildings in the area in and around Shinjuku Station. The pre-war form of Shinjuku, and the rest of Tokyo, for that matter, was retained after the war because the roads and rails, damaged as they were, remained, and these formed the heart of the Shinjuku in the post-war construction. Only in Kabuki-cho was a grand reconstruction plan put into action.
The present ward was established on March 15, 1947 with the merger of the former wards of Yotsuya, Ushigome, and Yodobashi. It served as part of the athletics 50 km walk and marathon course during the 1964 Summer Olympics.
In 1991, the Tokyo Metropolitan Government moved from the Marunouchi district of Chiyoda to the current building in Shinjuku. (The Tokyo International Forum stands on the former site vacated by the government
