In the late 1950's Ford saw sales of its 2 seat Thunderbird decline and in 1958 introduced a new larger 4 seater version which after its introduction in 1958 was incredibly successful.
Ford-Mustang 2011 SEMA auto show
Ford-Mustang 2011 SEMA auto show
In 1964 Ford produced the first Mustang and Chevy and Pontiac would be the only manufacturers to try to offer a close competitor. The Chevy Camaro and Pontiac Thunderbird were able to gain a decent amount of market share, but never became as popular as the original pony car. By 2006 the Mustang would be the only one of these 3 cars in production, although the Camaro would come back in a few years.