Two Thousand Maniacs
(1964)

Two cars with six passengers are lured on a fake detour through the small Southern town of Pleasant Valley.  The town folk tell them that they are there to be guests of honor at the town centennial celebration.  The "guests" are separated, and suffer gruesome deaths.  It turns out the centennial is the anniversary of when the town was destroyed by Union troops in the civil war.  On the 100th anniversary they want to kill Northerners in revenge.

The flirtatious blonde is chopped to pieces with an axe.  Her drunk husband is pulled apart by four horses.  The man who drove the car is rolled down hill in a barrel studded with sharp nails.  His wife is crushed under a huge boulder.  

The hitchhiker finds a plaque commemorating the destruction of the town in the Civil War.  He figures out what the town is up to.  He rescues the single lady, and the two of them escape through the woods.  He returns with a sheriff, but the town has disappeared.  

A final conversation reveals that the entire town died in the civil war. They come as ghosts for one day to get revenge.

Thanks Joseph C!