Background

The first line had been built and operated by the Buenos Aires and Pacific Railway, a British-owned company. The original projects included a railway to connect Argentina and Chile, but instead the BAPR focused on getting access to Buenos Aires. When the Government of Argentina granted concession to build the line, the company opened a 100-km length Mercedes−Palermo segment.

Ferrocarriles Argentinos

On 13 February 1947, the Government of Argentina acquired the Buenos Aires and Pacific Railway, changing its name to Ferrocarril General San Martín one year later when the entire Argentine railway network nationalised by Juan Perón's administration. Immediately after nationalisation, there was a project to electrify the line, however this never came to fruition.

During the 1960s the line was restructured, renewing its rolling stock. Therefore, the steam locomotives of San Martín line were replaced by diesel ones. The old coaches made of wood were also replaced by new wagons manufactured in Fiat Ferroviaria (then Materfer) factory in Córdoba Province.

In the 1970s the modernisation continued, renewing signals and rail tracks. In addition, most of the stations were remodelled while the orange colour was adopted to identify the line.

In 1978 a restructuring of the San Martín line was carried out by the de facto Military Government, so the terminus was set in Pilar, Buenos Aires Province. From that point on, Doctor Cabred (former terminus) and intermediate stop Manzanares were used for long-distance services exclusively, something which was reverted in later years.

Privatisation: Metropolitano

With the privatisation of the entire rail network led in the early 1990s by President Carlos Menem, Ferrocarriles Argentinos ceased to operate metropolitan services. A new State-owned transitional company, Ferrocarriles Metropolitanos S.A., was created to operate those services until they were privatised.

On 1 March 1994, private company Metropolitano (TMS) took over the line, which it operated until 7 January 2005, when the contract was revoked by the Government of Argentina. In spite of the large government subsidies received by TMS, a serious decline in the standard of their rail services has led to the original concession being revoked and the service was taken over by the consortium UGOFE.^[4]

Transition

With the line managed by UGOFE, several projects were announced to improve the San Martín line services, with an estimated 36 million passengers transported yearly and which were seeing an annual increment of 15% in ridership. In 2008 the Government of Argentina announced that the electrification using overhead lines for the whole system was to be started in June 2008. The project also included a new maintenance yard, new tracks for the entire line with all level road crossings to be eliminated and replaced with bridges and tunnels. .^[5][6] New rolling stock consisting of 24 diesel-electric CSR SDD7 locomotives and 160 coaches arrived from China to serve the line, which raised questions about the line's electrification.^[7]

On February 12, 2014, the operation of San Martín Line was granted to private company Corredores Ferroviarios.^[8][9] In April of the same year the San Martín line completed the modernisation of its entire fleet, putting into service 24 CSR SDD7 diesel locomotives and 160 coaches acquired from Chinese company CSR.^[10][11] The units had been bought in 2008 but they were unable to run so the stations had to modify their platforms for the new coaches. Once works were concluded, the Chinese trains made their debut in Argentina.^[12] The new rolling stock completely replaced the Materfer trains built in the 1960s and 1970s.^[13]

Renationalisation

State-owned company Operadora Ferroviaria Sociedad del Estado took over Belgrano Sur and Roca (operated by Argentren) and Mitre and San Martín (operated by Corredores Ferroviarios) lines after the Government of Argentina rescinded the contracts signed with both companies on March 2, 2015. The contract terms specified that the concession could be cancelled with no right to claim compensation.^[14] The agreements had been signed in February 2014, committing Argentren and Corredores Ferroviarios to operate the lines.^[15][16][17]

Expansion

In December 2014, plans were made between the Ministry of the Interior and Transport and City of Buenos Aires to elevate the entire line using a new viaduct from La Paternal station to the existing viaduct at Palermo station, together with a similar project for the belgrano Sur Line. Both governments cited benefits such as the improvement of road traffic and rail frequencies as reasons for building the 4.9 km (3.0 mi) viaduct.^[18]

The section from Retiro to Villa del Parque (set as provisional terminus while works were in progress) was closed in 2018,^[19][20] as a new viaduct (with an extension of 5 km) was being installed between intermediate stations Palermo and La Paternal to eliminate 11 level crossings in the city. Villa Crespo (formerly, "Chacarita") was closed in 2017 and La Paternal one year later.^[21] The viaduct was inaugurated in July 2019,^[20] although the covid-19 pandemic caused works were delayed so both stations remained closed.^[22] La Paternal was reopened in July 2022,^[23] while Villa Crespo remains closed as of May 2023.^[24]

In 2023 it was announced that the branch connecting the Caseros and Haedo stations (which had been abandoned for decades) would be re-opened for passenger services. Three new stops would be built for that purpose.^[25][26] The branch had been built and opened by the Buenos Aires Western Railway in 1908, connecting the San Martín, Roca and Sarmiento lines.^[27] As of 2023, the tracks are run only by freight services operated by Trenes Argentinos Cargas.^[28]

Historic operators

Companies that have operated the San Martín Line since it was established after the 1948 nationalisation are: