The significance of Mingo Jct is that it became the last home for big Alcos on Conrail. The LV C628s were sent there, as were the ex-PC and ex-RDG C628s 630s and 430s shortly after the April Fools Day merger. Some of the PC units were already based there IIRC.
Mingo's located in the WV panhandle, on the Ohio River maybe an hour or so west of Pittsburgh. Very much steel mill country at the time, less so now. Most of that trackage has been spun off since then.
From an operational standpoint, it made sense--there was a lot of ore traffic from the Lake Erie docks down into the Pittsburgh area at the time, and that was the kind of slow, pull your guts out service that the Alcos did best. Likewise with coal and coke going into the mills.
The Mingo assignment was not exclusive, however. I saw at least one freight coming down the Mohawk (NYC main) in 1978 with a lashup of PC C630 and a C636. CR had serious power problems in its early years, and units could be found very far from their intended service areas.
BTW, am I misunderstanding a previous post that all but two LV C628s were still in the Black and white snowbird scheme until the merger? Not true, most were in Cornell Red (which I prefer). Might have only been two left that had NOT been repainted by then.