The Shinjuku City of today was born on March 15, 1947 when what were originally the wards of Yotsuya, Ushigome and Yodobashi, merged. Although the wards of Yotsuya and Ushigome were born in 1878 as one of the 15 cities of Tokyo, Yodobashi was still divided into the towns of Yodobashi, Okubo, Totsuka and Ochiai in Toyotama County.
With urbanization, the population of the four towns grew by 62% in 1930 compared to 1920, and the difference in administration between the city and county grew obvious. For this reason, the movement to merge into wards began and the aforementioned four towns merged to become the ward of Yodobashi in October 1932. At around this time, the Shinjuku Station area was bustling with department stores, movie theaters, theaters and cafes, and Shinjuku grew as large downtown areas to outshine Yotsuya and Kagurazaka, the downtown Yamanote area which was famous since the Meiji Period.
The Tokyo Air Raid from May through August in 1945 transformed the city. The pre-war downtown areas of Shinjuku Station, Yotsuya, Kagurazaka and Takadanobaba became mere burnt fields, and most of the city was burnt to the ground. While there were 63,295 buildings in the former three wards before the war, 56,459 buildings were lost because of evacuation and damage during the war, leaving only 6,836 buildings. In addition, while the population was nearly 400,000 before the war, it was reduced to 78,000 at the end of the war.
This city has steadily grown step by step toward restoration from this kind of chaos. In other words, with the reformation of the constitution aiming for a democratic nation and accordingly, there was a revolution of local governments and Shinjuku City was born in March 1947 March with the merging of the three wards of Yotsuya, Ushigome and Yodobashi.

The History of the Names of the Three Areas of Shinjuku City;

Yotsuya:
Originally, a bleak part of the Musashino Plains, the area where Yotsuya Yonchome Intersection is today used to be a single road with nothing but deep thickets and valleys on either side. Then, four teahouses where travelers could rest were established. It is said that the name Yotsuya as we know it today with the characters for “four valleys” evolved from the name Yotsuya with the characters for “four shops.”

Ushigome:
The word kome means to be crowded, and it is said that this name came about because long ago, there were many cows put out to graze in this area. Lord Ogo of the State of Kozuke (what is now Gumma Prefecture) came to live in this area, and called himself Ushigome about 450 years ago in 1555. Lord Ushigome was affiliated with Lord Hojo of Odawara, and owned the land from Ushigome to Hibiya, and the castle was located on the plateau of the Fukuro-machi area. The grave of Lord Ushigome is still located in Sosan-ji Temple (1 Benten-cho).

Yodobashi:
It is said that the name of the bridge crossing over the Kanda-gawa River that flowed between Naruko-mura and Nakano-mura evolved from being called Yodo- (extra) or Yodokoro- (four places) Bashi (bridge). It is also said that when the third shogun, Tokugawa Iemitsu, was resting by the bridge during the Kan-ei period, he thought that the flow of the river seemed to be almost stagnant (yodomu), and decided to call the bridge Yodobashi. There is also a story that the eighth shogun, Tokugawa Yoshimune, named the bridge Yodobashi during the Kyoho period because the scenery reminded him of Yodo in the State of Yamashiro (what is now Kyoto). There are also various other stories, all of which seem to explain how the name of the area evolved from the name of the bridge.