The need to equip the city with an underground transportation network that would provide low-cost mobility for workers was a theme discussed and approached in a range of different studies in the early part of the 20th century. The project of a metropolitan rail system for Milan, abandoned due to the wars and lack of funds, was finally implemented in the years of the economic boom. The work on the M1 began in May 1957 on Viale Monte Rosa and launched a work of engineering and industrial production that involved not only the Società Metropolitana Milanese founded by the Municipality in 1955, but also companies of experts in structural engineering and consultants on foundations and earth mechanics from the Milan Polytechnic, who joined forces to develop the “Milan Method,” an open-air excavation system later exported all over the world, also partially utilized for the making of the Green Line (Linea 2, 1969). To cover the costs, which far exceeded the resources available to the city administration, twenty-year bonds were offered for a total of 30 billion lire, an offering open to all Milanese citizens, who took part with great enthusiasm and the «conscious desire to independently solve a problem that otherwise would still be a dream or just a project,» said the mayor at the time, Pietro Bucalossi. In November 1964 the official opening ceremony was held, after which the first trains began to run from Piazzale Lotto to Sesto Marelli, on the northern outskirts of Milan, along an overall line of almost 12 kilometers, for a total of 21 stops. In 1966 the second branch of the line was completed, to the southwest, as far as Piazza Gambara, followed in 1979 by the new terminus points of QT8 and Inganni, now extending as far as Bisceglie (since 1992) and Rho Fiera (since 2005).
The signage and interiors of the metro stations were designed by the studio Albini-Helg in collaboration with Antonio Piva and Bob Noorda for the graphics. The intuitive and functional simplicity of the project, winner of the Compasso d’Oro in 1964, became a model of reference for many other metropolitan rail systems, so much so that Noorda, residing in Milan since 1954, was later hired to design the coordinated image of the subways of New York and São Paulo. In spite of the very limited possibilities of intervention on an already established work of architecture, Albini and Noorda developed a very rigorous work of strong identity, a highly legible approach that blends architecture, furnishings, lighting and graphics in a coherent whole, making use of innovative and easily obtainable materials, paced by the red of the handrails and the signage bands of the mezzanines showing the names of the stations in a special font reworked by the Dutch designer. Today Milan has the most extensive public transport network in Italy, with 4 metropolitan rail lines, 5 suburban lines connecting the city to its surroundings, intersecting the main rail stations, and over 120 bus, streetcar and trolley bus lines.