Often, car companies like to give us hints at their future through their concepts. Sometimes, these prototypes aim to break established boundaries, while others pay homage to iconic models from the past and show us how a modern-day version could look like. Since these cars are not required to cover all tedious requirements a production version has to, the designers can go crazy with their creativity. Its no surprise then that concept cars are often the biggest head turners at car shows. Although every car brand has its own portfolio of interesting concepts, some of the most epic automotive art comes from the USA. Sadly, for one reason or another, many of these aesthetic and technological marvels remained prototypes. Here are some of the greatest American cars that never made it into production.