December 29, 1959: Opening of the original Lisbon Metro network with a Y shape. Common branch stations: Restauradores, Avenida, Rotunda (former name of the Marquês de Pombal station and where the line would split into the two branches). Current Blue Line branch stations (coming from Rotunda station): Parque, São Sebastião, Palhavã (former name of the Praça de Espanha station) and Sete Rios (former name of the Jardim Zoológico station). Current Yellow Line branch stations (coming from Rotunda station): Picoas, Saldanha, Campo Pequeno and Entre Campos.
March 1, 1998: Palhavã station is renamed to Marquês de Pombal, Sete Rios station is renamed to Jardim Zoológico and Socorro station is renamed to Martim Moniz.
Construction has started to add two new stations (Santos and Estrela), connecting the Green Line at Cais do Sodré to the Yellow Line at Rato and creating a circle line with the merger of the Green Line between Cais do Sódre and Campo Grande and the Yellow Line between Rato and Campo Grande.[3]