After a few years of running the initial electrified district with a dozen boxcabs the PV&T decided that it would be sensible to electrify the rest of the railway. So they placed an order with GE for a series of general purpose freight locomotives along the lines of the CMStP&P’s boxcabs, but faster (2 semi-permanently coupled 1800hp B+B units, to make a single B+B+B+B 3600hp locomotive.)

The first class B’s arrived in 1920 and allowed complete electrification of the busy Portland to Montréal mainline, as well as most of the traffic on the Augusta and Boston branches.

In 1930, when the second order of class Bs started to arrive, the first generation units were reclassified as class B1 & B1s.

The class remained intact (except for 221 & 224) until the early 1960s, when declining online traffic made it possible to retire some of the more worn units and two of the B1s switchers were rebuilt as class E prototypes.

As of 2023, only one of the (non-remanufactured) original class B’s remain – the class engine is still operating, but is earmarked for the historical fleet when it is no longer economical to keep in service (you’d think that one hundred and three years is the definition of no longer economical, but the Portland shops is really good at keeping things operating.)