Tocks Island Dam.
http://en.wikipedia.org/wiki/Tocks_Island
Basically back in the 60's and 70's the Corps of Engineers was going to build a dam on the Delaware River between NJ and PA. They forced a bunch of people out and then never built the dam. The area has been abandoned since. If you look at a map of NJ, you'll notice there are no towns along the Delaware north of Rt. 80.
If you take the last exit on Rt. 80 and drive north for about 20 miles, you'll come across some of the abandoned towns.