Harpers Ferry is a National Historical Park which means they try quite hard to keep the roads, the buildings and everything else as authentic as possible.
They're not crazy enough to try and maintain oil street lamps though. So while these look authentic when they're off, the light comes from a bulb. And in the name of energy conservation (and saving money) in this case it's one of those curly fluorescent bulbs.
I love the contrast inherent in this lamp.