The construction of the line, part of the ″direttissima″ Rome–Naples, was begun in 1911 and after a suspension during World War I, it was completed in 1925 between Pozzuoli and Piazza Garibaldi, electrified with third rail. Two years later the ″direttissima″ was completed, and the electrical rail service was extended towars Villa Literno and Gianturco.
In November 1935 the line was also electrified with overhead line; the third rail was discontinued in 1938.
In 1997, the line was numbered as Line 2, while the proper metro line became Line 1. The two lines were connected with a pedestrian tunnel between Museo and Cavour in 2002.