1960s America saw a shift in the American psyche as the first Baby Boomers came of age and automakers kept building bigger and more powerful cars. But while GM and Chrysler built cars for the parents of Baby Boomers, Ford was the first company to build a car specifically targeted at Boomers themselves.

That car was the Ford Mustang, and it was smaller, lighter, and more customizable than any other car on the market at the time. But before the first Mustang ever rolled down a production line, there was a series of concepts and sketches including the Mustang I concept which debuted in 1962. The Mustang I was a four-cylinder, mid-engine, two-seater designed to be a cheaper alternative to the Thunderbird, though ultimately Ford execs decided that four seats, not two, made more sense for coming-of-age Boomers.

The Mustang II concept, which was actually based on a pre-production Mustang body, was a lot closer to the final car than the Mustang I concept. When the final production model made its debut at the 1964 World’s Fair, it was an instant hit with young people all across America, and the almost innumerable options allowed Ford to reap massive profits from every sale.

Initially available with a 271-horsepower, 289 cubic-inch “HiPo” V8 engine that little V8 gave the Mustang a lot of punch as well as smaller six-cylinder offerings, the Mustang had something for everyone. Young men flocked to the Mustang to differentiate themselves from their fathers, who drove much bigger cars with much bigger engines that weren’t any faster, while young women opted for six-cylinder convertibles in one of the many feminine-leaning colors. The first person to ever buy a Mustang was a woman, and its appeal to the fairer sex definitely helped sales explode.

The immediate success of the Mustang gave birth to a wide range of variants, most famously the Shelby Mustangs, which kicked after Ford approached Shelby about a Mustang racing program. Though Shelby himself had doubts that the Mustang could be made to perform at a competitive level, he still took on the project, building the famous GT350. Shelby basically yanked everything not essential to racing from out of the Mustang while tuning the 289 V8 up from 271 hp to 306 hp. He also added a heavy duty rear-end from the Ford Galaxie and massive brakes, making the Mustang a very competent corner carver.

By 1966, Ford started rolling out the first High Country Edition Mustangs in Colorado, Wyoming, and Nebraska, and soon other special editions, like the California Special, followed. These regional special editions proved increasingly popular as well, helping generate even more profits.

In 1967, Ford redesigned the Mustang and introduced what today may be the most popular and desirable models. Fastback 1967 and 1968 Mustangs became forever ingrained in our national psyche thanks to movies like Steve McQueen’s Bullitt, which also packed the first big-block V8 in a Mustang, a 390 cubic-inch monster motor rated at up to 325 horsepower that let the Mustang rip off 13-second quarter-miles.

Ford didn’t stop there, a new 302 cubic-inch V8 was also offered alongside a massive 428 cubic-inch Cobra Jet engine, which made the Mustang a monster on the drag strip. Unfortunately the Mustang also went through the first of three growth spurts during the 1967-68 model years, getting longer, wider, and heavier. But neither buyers nor tuners like Shelby were concerned, and this model year led to the introduction of the big-block powered Shelby GT500s, which got the 428 Police Interceptor V8.

This growing trend carried into the 1969 model year, when another body style change made the Mustang even bigger. A heavier car called for bigger engines and more performance parts, and Ford introduced even more performance packages, like the Mach , which introduced both styling and performance enhancements at an affordable price.

Then there were the 1969 BOSS 302 and BOSS 429 Mustangs, which were built and sold to allow Ford to compete with their factory-built race car in the Trans Am and NASCAR racing series, respectively. The BOSS 302 proved especially capable of racing, offering track options like a posi-rear end, heavy duty suspension, and during the 1970 racing season, Parnelli Jones took a BOSS 302 Mustang to the championship that came down to the wire.

While the bigger BOSS 429 Mustangs never had the same racing success, today these cars are incredibly valuable, with well documented and restored variants regularly selling for well over $100,000. These cars featured no air conditioning because of the engine’s massive size, and could only be had with a manual transmission. Just 859 Boss 429s were built, making them some of the rarest Mustangs out there.

Unfortunately, 1970 would prove to be the high-water mark for the first-generation Mustang, and the last year for any serious performance. Not only had the base-model Mustang gained almost 700 pounds between the 1965 and 1969 model years, but new insurance regulations and emissions laws made muscle cars more expensive and less powerful. Less power plus more weight equaled a car fewer people wanted to buy, and sales dropped off dramatically.

The 1971 Mustang, the biggest one yet, featured dramatically-reduced performance from previous models. Ford widened the Mustang by another three inches over the already-wide 1970 models to accommodate without improving the suspension, and also introduced a BOSS 351 engine based on the new 351 Cleveland engine. By 1972 both Boss engine options were dropped due to tightening emissions regulations. The first-generation Mustang went out with a whimper, as the 1973 model year dropped any pretense of performance and customers flocked to smaller cars, like the Pinto, as gas prices soared.

Thankfully, a redesign faithful to the Mustang’s original mission was just around the corner for 1974, and today first-generation Mustangs still draw big bucks and massive amounts of attention. The Mustang II was a different story entirely, however.