Under Construction, but here's some Wkipedia on the early origins of Stock Car Racing:
Early stock car racing
In the 1920s and 1930s, Daytona Beach became known as the place to set world land speed records, supplanting France and Belgium as the preferred location for land speed records, with 8 consecutive world records set between 1927 and 1935. After a historic race between Ransom Olds and Alexander Winton in 1903, the beach became a mecca for racing enthusiasts and fifteen records were set on what became the Daytona Beach road course between 1905 and 1935. By the time the Bonneville Salt Flats became the premier location for pursuit of land speed records, in 1936, Daytona beach had become synonymous with fast cars. Drivers raced a 1.5 to 2-mile (3.2 km) stretch of beach as one straightaway and beachfront highway A1A as the other.
Stock car racing in the United States has its origins in bootlegging during Prohibition, when drivers ran bootleg whiskey made in Appalachia region of the United States. Bootleggers needed to distribute their illicit products, and they typically used small, fast vehicles to better evade the police. Many of the drivers would modify their cars for speed and handling, as well as increased cargo capacity, and some of them came to love the fast-paced driving down twisty mountain roads. One of the main 'strips' in Knoxville, Tennessee, had its beginning as a mecca for aspiring bootlegging drivers.
The repeal of Prohibition in 1933 dried up some of their business, but by then Southerners had developed a taste for moonshine, and a number of the drivers continued "runnin' shine," this time evading the "revenuers" who were attempting to tax their operations.  The cars continued to improve, and by the late 1940s, races featuring these cars were being run for pride and profit. These races were popular entertainment in the rural Southern United States, and they are most closely associated with the Wilkes County region of North Carolina. Most races in those days were of modified cars. Street vehicles were lightened and reinforced