It's on the old Baltimore & Ohio Railroad mainline between Cumberland, Maryland, and Pittsburgh, Pennsylvania. It's the start of the grade for westbound trains.
Trains headed west toward Chicago from Cumberland follow Wills Creek out of town. At Corriganville, Maryland, they make a turn to the right and head north. They soon cross the Mason-Dixon Line, with Hyndman the next population center. So far, the trains aren't gaining much altitude. At Hyndman, though, some trains have helpers (extra locomotives) added so they can make the climb to the top of the grade, at Sand Patch, Pennsylvania.
Cumberland is at about 540 feet altitude, and Hyndman is probably 600- or 700-something feet up. Sand Patch is over 2200 feet in altitude, so there's some serious climbing ahead.
Q388 was an eastbound train, headed downhill. He would have been in Cumberland in another half-hour or so.
Forty years ago, I could go up there and have the place all to myself. I could spend the entire weekend and not see another railfan, or train enthusiast.
Since then, the line has become popular with railfans. A website, Trainorders, has a video camera stationed there so that people at work - I mean, at home - can watch trains going through Hyndman.
Here's the link to the webcam: https://www.trainorders.com/videos/sandpatch/. In some of those scenes, you can see the stopped train. You are looking north, toward the rear of the train. You can see smoke from the burning cargo in the distance.
Here's the story at Trainorders: Eastern Railroad Discussion > CSX Q388 on the ground & on fire
The article will help you find a scanner feed so that you can listen to the agencies responding to the derailment.
Full disclosure: I own shares of CSX.