Strasburg keeps a pretty nice little fleet, along with #90. SRC #31, a former Canadian National 0-6-0, was the first engine to return steam power to the Strasburg in the 1960s. They tore it down for an overhaul a few years ago and have been so busy with customer work that they haven't had time to really work on the #31. On top of that, the #31 was pretty rough riding, and beat the tracks up as well, and with other engines on hand, its not a huge priority for them. When I was there, the cab was sitting outside the shop, and the boiler was off the frame.
Strasburg #89 is an ex-Canadian National 2-6-0. Its history is a bit of an unknown, but Nelson Blount, who founded the original Steamtown, picked it up in the '60s and it was a favorite of his right up until his death. It came to Strasburg in the '70s and has been their main locomotive since. It's just the right size for their operations. It has a PRR "Banshee" whistle on it, which is cool
Strasburg #475 is an unusual beast, one of Norfolk & Western's M-Class 4-8-0 "Mollies". There are only a handful of them left and it's the only operational one in existence. It's also Strasburg's oldest engine in existence (built in 1906) and one of their more recent acquistions, coming to them in 1991 in very rough shape
Also on the property is Reading #1187, one of only 3 Camelbacks to survive. They ran it back in the 1960s, but even then it was too small, and Camelbacks are sort of dangerous equipment. They parked it in 1967, and it has sat at the railroad museum across the street since then, looking a bit bedraggled these days, but there plans for a long-term cosmetic restoration.
Canadian Pacific 4-6-0 #972 is even worse. They received this engine from Rail Tours Inc. in Jim Thorpe after the RTI couldn't afford the repairs that Strasburg had been performing. At one point they considered restoring it to operation but it apparently needs every last nut and bolt, and they don't have much interest in it.
They also have an EMD SW9 that belonged to the New York Central. They acquired it in 2018 to replace their retired GE 44-tonner and handle the small freight renaissance that they are currently experiencing (~10 cars a week).
They also are working on an LIRR/PRR G5 4-6-0 with a 48-year lease once its operating.