In the past, the line started from Sanjo Station (Kyoto Prefecture)--which was also used by the Keihan Main Line but later became independent from the Keihan Main Line and was renamed as Keishin Sanjo Station--passed a steep incline of 66.7 per miｌ, equivalent to Usui-toge Mountain pass or the Tokyu Tamagawa Line, located near Keage Station (Keihan), ran on a track on streets to Misasagi Station and ultimately connected Kyoto and Otsu; however, on October 12, 1997, its portion of Misasagi Station westward was abolished and the line was directly linked to the Kyoto Municipal Subway Tozai Line.
かつては京阪本線と共通の三条駅(京都府)（後に同線から分離して京津三条駅と改称）が起点で、蹴上駅(京阪)付近では碓氷峠や東急玉川線並みの66.7パーミルの急勾配を越え、御陵駅までは併用軌道も交えて京都・大津間を結んでいたが、1997年10月12日に御陵駅以西が廃止され、京都市営地下鉄東西線へ乗り入れを開始した。