東京23区の名前のついた
すべての坂を網羅する予定のサイト

 古くは飯田坂と呼ばれていました。名前の由来は、坂に沿って御用屋敷の長屋が九つの段に沿って立っていたためとも、急坂であったため九つの段が築かれていたからともいわれています。明治後期、九段坂下から市ヶ谷方面に市電を通すため、牛ヶ淵(北の丸公園に沿った堀)側の勾配を削って線路を敷設しました。
 関東大震災後の帝都復興都市計画で坂を大幅に削り緩やかな勾配にする工事が行われ、九段坂は大正通り(現在の靖国通り)として東京の主要な幹線道路の一部となり現在に至ります。

 In the past, this was called Iida Hill. It is said that the nagaya (a number of tenement houses built under on long roof) of the official residence were built on nine levels (kudan) along the hill, and that nine levels were constructed due to the steepness of the hill, hence the name the Hill of Kudan. In the late Meiji Period(1868-1912),in order for trams ran from the bottom of the Hill of Kudan to Ichigaya, the gradient of the Ushigafuchi side (the moat that runs aling kitanomaru (the west keep) park) was reduced, and the tracks were constructed.
 The Imperial Capital Construction Plan after the Great Kanto Earthquake of 1923 carried out construction work that greatly reduced the hill, and created a gentle gradient.
The hill of Kudan is even now an important part of the main througfare in Tokyo as Taisho-dori(now Yasukuni-dori).