The idea behind the project was ambitious: in 1967, the Bonn city council decided to create a fast connection between the government district, Bonn and Bad Godesberg.
With a budget of around 203 million marks, the project was one of the largest urban infrastructure projects of the time.

The tunnel section alone accounted for 190 million marks, or just under 6 million marks per kilometer of tunnel. Most of the costs were covered by the federal and state governments, with the city of Bonn covering 10 percent of the costs.

The construction: a major challenge

On October 12, 1967, the first pile-driving took place at the corner of Erste Fährgasse and Adenauerallee. Not only Bonn politicians were present at the time, but also the former state transport minister Hermann Kohlhase, his federal counterpart Georg Leber and the then finance minister Franz-Josef Strauß. Construction of the tunnel began below the Post Ministry, which was located there at the time, between Bundeskanzlerplatz and today's Hauptbahnhof stop, which was only used as a turning area in the first years of the light rail system.

The terminus of the trains was initially the temporary stop 'Am Hauptbahnhof'. It was not until 1979 that the current main station stop with its four tracks was opened. The tunnel was partly built using the cut-and-cover method. 650,000 cubic meters of earth were excavated, the equivalent of 140,000 truckloads. The route of the 3.2-kilometer tunnel was planned and built by several hundred specialists in 2.5 million working hours.

The pile-driving work on Adenauerallee shook the houses of local residents enormously. During this work, an unbureaucratic arrangement between a dentist on Adenauerallee and the crew of a heavy pile driver caused a sensation. If the dentist had to carry out a complicated treatment, he hung a red flag out of the window of his practice. The pile-driving operation was then stopped and the dentist was able to work undisturbed.

The big day in March 1975

Then the time had finally come: on March 22, 1975, the first train of the Bonn light rail went through the tunnels. At 10.28 a.m., the train set off on its maiden journey to the applause of the 500 people present. Light rail driver Josef Hansen, who was selected from a group of 20 drivers, had a particularly proud moment - after all, he was the first driver to drive the entire route. In addition to the obligatory vehicle number, the streetcars were given a name and a coat of arms. The first vehicle 7351 was named Bonn, the other streetcars were named after twin cities or cities with a subway railroad.

Representatives from the metro cities of Berlin, Hamburg, Frankfurt, Munich, Cologne, Nuremberg and Stuttgart traveled to Bonn for the christening of a further seven light rail vehicles with the names of the partner municipalities. At the opening of the new subway line, the respective light rail vehicles were christened with typical drinks from the respective regions by the Mayor of Bonn: Berliner Weiße, Kölsch, Äbbelwoi, Württemberg wine, Bavarian wheat beer and Franconian smoked beer were used for this. On Saturday and Sunday, 37,000 guests attended the subsequent opening ceremony for the Bonn subway on Bonn's market square and the information show at the station.