MBTA running hours (historical operation times)

Has the Subway lines in Boston historically always ended at 12AM even before the MBTA was created? Like in the 1920s did the red line (whatever it was back then) run say 24/7?

The Cambridge-Dorchester line (Red Line) built in several stages from Harvard to Ashmont and the Mainline Elevated & Washington Street Tunnel which was the predecessor of today's Orange line did not operate from about 12:30 am to about 5 am or so, slightly later on Sundays. During those hours Night Cars were run on various routings into the trolley subway. These cars had some very long routes from the farthest outer edges of the system in Dorcester/Hyde Park/W Roxbury all the way Downtown. Some routes ran on hourly times, others 30 min. All routings met simultaneously at the Scollay Station (Government Ctr). Down below, 3rd rail trains of what is now the Blue Line, ran on 30 minute headways to Maverick Station. Maintenance was performed on the Cambridge-Dorchester and Mainline during those hours.

Interesting EdBear. Do you know how they managed maintenance on the tremont/boylston subways along with the East Boston tunnel?

Someone once posted an image here showing the number of trains entering park street at all times in the day.

Even at 3 am, there was a train (trolley) every 5 or so minutes providing service.

I don't really know how the trolley subway tunnels were maintained, but I think it was a bit easier to work there even under traffic in the wee hours because there is no third rail. In addition for several decades up into the 1920s, there was some surface track in the Downtown area which probably could be used for some diversions. By the 1920s, the bus was available for trolley subway shutdowns for maintenance. I have no idea how the Scollay-Maverick night mainenance was done.