The line was opened on April 5, 1964, between T-Centralen and Fruängen and Örnsberg.
Several more sections were opened between 1965–1967, while the last extension to Mörby centrum was completed in 1978.
Within Stockholm's inner city, the red line was built independently of the street network, and at a greater depth than the Green line, which was constructed mainly under roadways.

The Mälarhöjden-Liljeholmen section had its origins as the Södra Förstadsbanan tramway, dating from the 1910s.
The somewhat newer Liljeholmen-Midsommarkransen section was built primarily on its own right of way, as the area was not densely populated.
However, there were level crossings and subsequent sections were built in tunnel before the start of the metro.
Today not much is left of the original tram route.

The Telefonplan–Fruängen section (lines 14 and 17) was built in 1946–1956 as a pre-metro, with high-level centre subway platforms and shorter, low-level tram platforms at the sides.
This section is the same today.
For the extension beyond T-Centralen, tunnels had already been built when the Green line was built there, mostly by the cut-and-cover method.
T-Central station was opened in 1957 for the Green line, while the Red line platforms opened in 1964.
The route between Fruängen and Mörby centrum and back was originally numbered line 24, but was renumbered 14 around 2001.

The Liljeholmen-Fruängen section underwent major renovation during the summer of 2006.
The service was temporarily replaced by a bus route.
The line was opened on April 5, 1964, between T-Centralen and Fruängen and Örnsberg. Several more sections were opened between 1965–1967, while the last extension to Mörby centrum was completed in 1978. Within Stockholm's inner city, the red line was built independently of the street network, and at a greater depth than the Green line, which was constructed mainly under roadways.
The Mälarhöjden-Liljeholmen section had its origins as the Södra Förstadsbanan tramway, dating from the 1910s. The somewhat newer Liljeholmen-Midsommarkransen section was built primarily on its own right of way, as the area was not densely populated. However, there were level crossings and subsequent sections were built in tunnel before the start of the metro. Today not much is left of the original tram route.
The Telefonplan–Fruängen section (lines 14 and 17) was built in 1946–1956 as a pre-metro, with high-level centre subway platforms and shorter, low-level tram platforms at the sides. This section is the same today. For the extension beyond T-Centralen, tunnels had already been built when the Green line was built there, mostly by the cut-and-cover method. T-Central station was opened in 1957 for the Green line, while the Red line platforms opened in 1964. The route between Fruängen and Mörby centrum and back was originally numbered line 24, but was renumbered 14 around 2001.
The Liljeholmen-Fruängen section underwent major renovation during the summer of 2006. The service was temporarily replaced by a bus route.
Red line (Stockholm metro)