Situated almost entirely above the former customs barrier around the capital (Boulevards extérieurs), it runs in a semicircle in the north of Paris.

Slightly over 2 km (1.2 mi) of the line is built on an elevated viaduct with four aerial stations.

In 1903, it was the location of the worst incident in the history of the Paris Métro, the fire at Couronnes.

On 30 March 1898 a déclaration d'utilité publique was published, recognising the public benefit of the first six planned lines of the Paris Métro.

In response, the city began rapidly constructing the first line in hopes of opening it in time for the 1900 World's Fair.