Harper's Ferry Map in 3D
The 3D view really brings out the height of the rock face behind lock 33. The Potomac is on the right, the Shenandoah on the left. The Sandy Hook Bridge (Route 340) is depicted as the double red line crossing the Potomac at the White Horse Rapids.
This 2D map is probably more useful for seeing the area around Harpers Ferry. Because of the very limited parking, if you decide to visit the town and take in the John Brown story, you'll need to park at the city lot and take the shuttle bus to the park. They get a lot of tourists though and the buses are fairly painless.