1904-1911: The great net extension
The general net plan of 1898 is updated in 1909. It intends in the final phase already 12 line branches going out from the city centre, an internal and external ring line as well as an essential - but never built - connection from the Hauptpost to the Gewerbeschule. To sum up, the most important distance extensions: In 1905 the tram goes to Allschwil, 1907 till Aesch (BL), 1908 to Riehen Kirche, 1910 across the boarder to Huningue gare (Germany, today France) and in 1911 the lengthening in St. Louis up to church.

1912-1922: I-st world war and a "speculation line"
In 1912: Opening of the stretches Gärtnerstr. - Wiesenplatz, Innere Margarethenstr. 1913: Missionsstr. - Lysbüchel 1914: Riehen - Grenze. The I-st world war stops the projects for tram lines in Baden and Alsatian border municipalities. The urban tram net is further built, but construction however slowed down. In 1915 the romantic line to the "Bruderholz" is built as a condition for the development of the Basel hillside. At the time it's still a green meadow. 1916: Johanniterbrücke, Hardstr. - St. Jakob 1919: Steinenring - Neuweilerplatz and Riehen Grenze - Lörrach Bhf. (D) 1922: Muttenz - Pratteln

1923-1944: Conclusion of the development to the "tram city"
On the 26th May, 1930 the first both coach lines are initiated: Claraplatz - Bettingen and Kleinhüningen - Claraplatz - cemetery am Hörnli. The stretch Kleinhünningen - Claraplatz is stopped again on the 17th December, 1934 with the opening of the tramline St. Johann station - Dreirosenbrücke - Mustermesse. Together with the segment Margarethenstr. - Binningen open in the 1934 the tram net in Basel reaches with 72 km its biggest expansion. On the 31st July, 1941 the coach line Claraplatz - Hörnli is changed to the first trolley bus line.