The Battle for Crampton's Gap
Spook Hill is on the outskirts of Burkittsville, Maryland.  The site was the setting of a Civil War battle that is known as the Battle for Crampton's Gap.  During that battle, Union soldiers had taken up position at the top of the hill overlooking Burkittsville with nothing more than their rifles.  The Confederate soldiers were unaware of the Union presence and began moving their heavy artillery from the town of Burkittsville and up the hill.  When the union soldiers sprung their ambush, the Confederate soldiers either were gunned down or quickly retreated, abandoning their artillery.

Ghostly Assistance?
For the years since, many people have driven to this hill and stopped and put their cars in neutral.  Rather than gravity pulling them back down the hill, their cars actually begin to move up the hill.  Some swear it is simply an optical illusion, while others insist it is the ghosts of the Confederate soldiers pushing the vehicle as they pushed their artillery so many years ago.  Accordingly, the hill has since been dubbed Spook Hill or Gravity Hill, depending on who you talk to.

It isn't recommended that you try this out.  It is a public road that is populated by other drivers, who might not be expecting someone to put their car in neutral to be pushed by the ghosts of Confederate soldiers.