The first tramway in Lisbon entered service on 17 November 1873, as a horsecar line. On 30 August 1901, Lisbon's first electric tramway commenced operations. Within a year, all of the city's tramways had been converted to electric traction.
Up until 1959, the network of lines was further developed, and in that year it reached its greatest extent. At that time, there was a total of 27 tram lines in Lisbon, of which six operated as circle lines. As the circle lines operated in both clockwise and anticlockwise directions, each with its own route number, it is more correct to speak of a total of 24 tram routes, all of them running on 900 mm (2 ft 11 1⁄2 in) narrow gauge tram lines.
Map of Tram tracks in Lisbon (network of 2011 in red)
The construction of the Lisbon Metro began the slow decline of the network. Although reports prepared by both the École Polytechnique Fédérale de Lausanne and the Verkehrsbetriebe Zürich concluded that the network should be retained and even extended, the process of decline has continued. However, some work has recently been done on preparing the Carmo–Campolide line for reopening.