no the SS is not the first muscle car. muscle cars were considred muscle cars when u took a larger sized engine, dumped it in a intermediate body and sold it at a low price. Since the GTO's were sold anywhere from 2-3.5k and with that price many people could afford them. On the other hand the Impalas were a nice car but that "nice" came with a higher price tag that many drivers couldnt afford so of course the turned to the smaller cars or went somewhere else. You can call the impala SS a muscle car all u want but it does not meet up to being a smaller car with a big engine and a low price. If im wrong guys, correct me.