The depot previous to the 1950s"trough" was built in the 1840s and, as a previous poster noted, was the granite castle station (Rockport granite, perhaps?). The ERR president at the time, David Neal if memory serves, had visited the UK (Wales, I think) and was so impressed with the castles he saw, he had the ERR replicate one as the Salem Depot. It was also ERR headquarters for a time. The castle depot was a big tourist attraction too, and befit the entry point for visitors to the Witch City. Hawthorne refers to it in "House of the Seven Gables" (1851).
But the castle depot had problems. The south end of the tunnel emerged at a grade crossing before plunging into the mouthed arch of the depot, meaning that dozens of times a day, grade crossing attendants had to flag traffic. City and railroad officials thought it was a real safety hazard. Pigeons also loved the old depot and pelted waiting passengers. I talked with some older Salemites about 20 years ago, and they remembered that the place was caked in pigeon droppings by the 1930s & 1940s. The railroad tried to demolish the place for a while, but not until the 1950s did it finally come to pass in a classic "urban renewal" program. The tunnel was lowered and slightly extended, I think (wasn't there a "high car job" freight previous to the mid-1950s because of the tunnel height?), the Riley plaza rotary was created on the site of the old depot, and the trough station built. I've seen a photo somewhere, probably an old Bulletin, showing a smiling Pat McGinnis opening up the new station via an RDC.
I did some research on the old depot when I was in high school back in the mid-1980s, and have it somewhere...
Here's a recent Salem Evening News article about it:
http://www.salemnews.com/permalink/loca ... 04011.html
Here's old postcard view here:
http://www.oldpostcards.com/d/dep-MA008.html