Line D was the second line to be built by the Compañía Hispano Argentina de Obras Públicas y Finanzas (CHADOPyF, Hispanic-Argentine Company for Public Works and Finances), following the construction of Line C in 1934. Construction began in 1935 and the first part of the line was inaugurated in 1937 and ran 1.7 km from Catedral (still the current terminus) to Tribunales. Three years later, the section which brought the line to Plaza Italia in Palermo was completed, bringing the length of the line to 6.5 km.