In 1871, eight main line railways existed in Berlin, with terminal stations at the city's edge or outside the city limits.
This was very impractical for many passengers, who were forced to use hackney carriages to transfer from one train to another.
Therefore, a railway line was planned to connect these terminuses with each other.

In 1872, the Deutsche Eisenbahnbaugesellschaft (German Railway Construction Company - DEG) filed the planning application for a railway line through the city, connecting the then-Schlesischer Bahnhof (today Berlin Ostbahnhof) to Charlottenburg, and continuing to Potsdam.
In December 1873, the state of Prussia as well as the private rail enterprises Berlin-Potsdamer Eisenbahn, Magdeburg-Halberstädter Eisenbahn and Berlin-Hamburger Bahn bought shares in the DEG, and jointly founded the Berliner Stadteisenbahngesellschaft (Berlin City Railway Company).
However, things did not go as expected and the DEG went into bankruptcy in 1878, which forced the Prussian state government to take over operations, pay for the construction of the line with state money and to reimburse the former private owners of the DEG.
The state's interest in the line was attributed to the military, which after the 1870-1871 Franco-Prussian War was of the opinion that the railway networks would hinder mobilisation when not properly interconnected.

On 15 July 1878 the Königliche Direktion der Berliner Stadteisenbahn (Royal Directorate of Berlin City Railways), under the management of Ernst Dircksen, was commissioned to manage the site.
The directorate at first reported to the Prussian Ministry of Transport and later became a subsidiary of the Ministry of Public Operations.

The planned railway had two tracks each for freight and passenger traffic.
Having taken similar projects in London and New York City into consideration, passenger traffic received priority over freight trains.
Furthermore, the new railway line was not only to serve as a connection between the mainline termini in Berlin, but would also offer connections to the Berlin Ringbahn and the suburban rail lines.

The traffic routing was not only influenced by the location of the already existing stations the line was supposed to connect, but also by land availability in the city centre.
One of the original drafts, which called for building the line along Leipziger Straße, had to be scrapped because of overly high land prices.
The moat of the 17th century Berlin Fortress was filled up between Hackescher Markt and Jannowitzbrücke stations and, since it was public land, was used for building the railway line.
This explains some of the curvy sections on the Stadtbahn, especially between Alexanderplatz and Jannowitzbrücke stations.

Its elevated nature sets the Stadtbahn apart from the previous Berliner Verbindungsbahn, built in 1851, which was built at street level and was a hindrance to travel.
In 1871, eight main line railways existed in Berlin, with terminal stations at the city's edge or outside the city limits. This was very impractical for many passengers, who were forced to use hackney carriages to transfer from one train to another. Therefore, a railway line was planned to connect these terminuses with each other.
In 1872, the Deutsche Eisenbahnbaugesellschaft (German Railway Construction Company - DEG) filed the planning application for a railway line through the city, connecting the then-Schlesischer Bahnhof (today Berlin Ostbahnhof) to Charlottenburg, and continuing to Potsdam. In December 1873, the state of Prussia as well as the private rail enterprises Berlin-Potsdamer Eisenbahn, Magdeburg-Halberstädter Eisenbahn and Berlin-Hamburger Bahn bought shares in the DEG, and jointly founded the Berliner Stadteisenbahngesellschaft (Berlin City Railway Company). However, things did not go as expected and the DEG went into bankruptcy in 1878, which forced the Prussian state government to take over operations, pay for the construction of the line with state money and to reimburse the former private owners of the DEG. The state's interest in the line was attributed to the military, which after the 1870-1871 Franco-Prussian War was of the opinion that the railway networks would hinder mobilisation when not properly interconnected.
On 15 July 1878 the Königliche Direktion der Berliner Stadteisenbahn (Royal Directorate of Berlin City Railways), under the management of Ernst Dircksen, was commissioned to manage the site. The directorate at first reported to the Prussian Ministry of Transport and later became a subsidiary of the Ministry of Public Operations.
The planned railway had two tracks each for freight and passenger traffic. Having taken similar projects in London and New York City into consideration, passenger traffic received priority over freight trains. Furthermore, the new railway line was not only to serve as a connection between the mainline termini in Berlin, but would also offer connections to the Berlin Ringbahn and the suburban rail lines.
The traffic routing was not only influenced by the location of the already existing stations the line was supposed to connect, but also by land availability in the city centre. One of the original drafts, which called for building the line along Leipziger Straße, had to be scrapped because of overly high land prices. The moat of the 17th century Berlin Fortress was filled up between Hackescher Markt and Jannowitzbrücke stations and, since it was public land, was used for building the railway line. This explains some of the curvy sections on the Stadtbahn, especially between Alexanderplatz and Jannowitzbrücke stations.
Its elevated nature sets the Stadtbahn apart from the previous Berliner Verbindungsbahn, built in 1851, which was built at street level and was a hindrance to travel.
Berlin Stadtbahn