When Ford rolled the Mustang off the floor and onto the auto market back in 1964, muscle car enthusiasts all over the United States paid attention. That’s why the car’s launch was the most successful in automotive history. While it would be easy to credit the car’s sleek and stylish look coupled with high performance features as the key reason why the car sold more than 1 million units in just 18 months, there were definitely other factors to the success of these premiere muscle cars.