In the sixties, the Long Island Railroad ordered a new generation of electric multiple units from Budd to replace their ageing pre-war units. They had to be much more comfortable, air-conditioned and be of lightweight construction. Due to the required speed of 100 mph or 161 km/h, the voltage of the third rail was increased from 650 to 750 V. Even the platforms in all stations had to be rebuilt to provide for high-level entry.

Each unit was composed of two four-axle cars with a 110 kW traction motor in each axle. Between 1968 and 1973, 770 M1 were built for LIRR. Penn Central got 178 more which were designated M1A. When LIRR got 174 more cars between 1984 and 1986, these were of an updated design and called M3. Now each traction motor delivered 120 kW. Metro-North ordered 142 of this design, which were called M3A.

Even though they were marketed as “Metropolitans” by Budd, they became known in the public under their class names M1 and M3. Due to signal and track limitations, they only reached 80 mph or 129 km/h in service. After the M3 was introduced, the M1 were refurbished and now looked similar in the inside. The last M1 was retired in 2009 and the M3 is still in service.