Someone once said auto racing began when the second car was built. For more than 100 years now, competition has driven both technology and sales in the car business -- hence the old industry maxim, "race on Sunday, sell on Monday." And it's true. That, in a nutshell, explains how muscle cars came to be.

Two types of motorsport play especially large roles in muscle car history. One is stock-car racing, which began coming together once some "good ol' boys" formed the National Association for Stock Car Auto Racing in 1947.

Inspired by the souped-up cars of Southern moonshine runners and their skill at escaping the law, NASCAR began staging races on dirt tracks and beach courses. These events drew crowds and soon developed into a thriving business. Other organizations, such as the U.S. Automobile Club, began sanctioning their own stock-car races.

Drag racing, meanwhile, was attracting its own fans. These organized contests of quarter-mile acceleration originated with the informal (and illegal) street racing associated with hot rodders, the shade-tree mechanics who turned old Model T and Model A Fords into fast, eye-catching street cars. Drag racing gained momentum in 1951 when the National Hot Rod Association was formed in -- where else? -- car-crazy Southern California.

At about the same time, NHRA chief Wally Parks started Hot Rod magazine to promote the sport and performance-tuned street cars. The early '50s also saw the debut of Motor Trend and other car-enthusiast magazines, the first of many.

The growing public interest in speed and power gave birth to what many regard as the first muscle machine, the 1949 Oldsmobile Rocket 88. It was a car any hot-rodder could understand: a powerful new engine in the lighter Olds body. And the engine was a breakthrough: America's first high-compression overhead-valve V-8, the result of research begun at General Motors well before the war.

Though GM's Cadillac Division introduced a similar V-8 for '49, it was the smaller, fleeter Olds 88s that grabbed public attention, especially when they started to dominate stock-car racing.

Because success in Detroit never goes unchallenged for long, the Rocket 88s soon had showroom competition and a horsepower race was on. By 1955, most every U.S. nameplate offered light, efficient V-8s. Two of the best remain performance legends to this day.

One was Chrysler Corporation's Hemi, first offered for 1951 and named for the half-sphere or hemispherical shape of its combustion chambers. No less significant was the 1955 Chevrolet small-block V-8, a design so right that its basic engineering concepts are still in production.

But the horsepower race wasn't always about sheer speed. Detroit would soon learn the importance of giving its hot cars names and marketing directions that matched their tire-smoking excitement.