The line started out with the section between Shin-Sakuradai and Kotake-Mukaihara, and began through operations with the TRTA (now Tokyo Metro) Yūrakuchō Subway Line. At this point, the line did not connect with any other Seibu Line, so only TRTA trainsets were used. In 1994, the line was extended from Shin-Sakuradai to Nerima, connecting with the Seibu Ikebukuro Line. Because of track elevation work at Nerima, only one track was used. Later in 1998, the section between Shin-Sakuradai and Nerima became double-tracked, and through services with the Ikebukuro Line began.[1]
Station numbering was introduced on all Seibu Railway lines during fiscal 2012, with Seibu Yurakucho Line stations numbered prefixed with the letters "SI" (part of the Seibu Ikebukuro group of lines).[2]
^"東京メトロ有楽町線が西武池袋線に乗り入れ開始した日 -1998.3.26" [On this day in 1998, through operation between the Tokyo Metro Yurakucho Line and Seibu Yurakucho Line begins]. trafficnews.jp (in Japanese). 26 March 2022. Retrieved 27 March 2022.
^西武線全駅で駅ナンバリングを導入します [Station numbering to be introduced at all Seibu stations] (PDF). News Release (in Japanese). Japan: Seibu Railway. 23 February 2012. Archived from the original(PDF) on 24 September 2015. Retrieved 27 March 2013.
^東急5050系が西武鉄道池袋線で営業運転開始 [Tokyu 5050 series enters service on the Seibu Ikebukuro Line]. RM News (in Japanese). Japan: Neko Publishing. 10 September 2012. Retrieved 10 September 2012.
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