Unfortunately I could not see any map that showed Clarksburg as a supercharger location (I don't know that those parking spaces are anything more than just reserved for low emission vehicles). It would be great to have one before Hagerstown. I have a sister in Frederick and I live in Richmond. Being able to charge on the 270 corridor would be great.
When you look compare the 2017 projection map to the current map there is definitely something between Laurel and Hagerstown.
Like Sir Guacamolaf said in post 306 "Looks quite clear that there is a supercharger planned for the 270/495 interchange, and another one in Frederick". To me, the location looks a little below Frederick and with Tesla's current relationship with Simon Properties it should be a easy spot to develop but hey I think either location would be fine.