In 1949, Smith took over the National Stock Car Racing Association (NSCRA), one of several fledgling stock-car sanctioning bodies and a direct competitor to the recently founded NASCAR, and announced that the series, which sanctioned races across Tennessee, Georgia and North Carolina, would establish a “Strictly Stock” division that year; some believe this caused Bill France, Sr., NASCAR’s founder, to accelerate his plans for his own Strictly Stock division, which would later become Winston Cup Series and is now known as the NASCAR Cup Series; it also touched off a rivalry between Smith and the France family.

In 1950, Smith took over a lease of Charlotte Speedway from Buck Baker, Roby Combs and Ike Kaiser to promote races there. The same year, France and Smith discussed merging their sanctioning bodies, and came to a tentative agreement on the issue; however, Smith was drafted into the United States Army to fight in the Korean War in January 1951, becoming a paratrooper. When Smith returned to civilian life two years later, he found that mismanagement in his absence had caused NSCRA to dissolve.

Smith built Charlotte Motor Speedway in 1959 for $1.5 million, with financing from his wealthy brother-in-law. Racer Curtis Turner helped with promoting the track. Smith went bankrupt two years later. The track was turned over by Judge J.B. Craven to local furniture store owner Richard Howard, who ran the track and worked it out of its debts (the mortgage was burned publicly in 1967) while Smith moved to Illinois, eventually buying out other shares of stock in the track to regain control in the early 1970s.

He later founded Speedway Motorsports, Inc. (SMI), which owns eight NASCAR tracks that host twelve NASCAR Sprint Cup events. Speedway Motorsports owns Charlotte Motor Speedway, Atlanta Motor Speedway, Bristol Motor Speedway, Sonoma Raceway, Kentucky Speedway, Las Vegas Motor Speedway, New Hampshire Motor Speedway, and Texas Motor Speedway. The NASCAR Sprint All-Star Race is also held annually at the Charlotte Motor Speedway. He shook up the motorsports world in 1995 when he took the company public and traded it at the New York Stock Exchange (NYSE). SMI was the first motorsports company traded at the NYSE.

Controversy broke out in September/October 2007 when Smith revealed plans to build a drag racing strip on land close to Charlotte Motor Speedway. Many residents living near the speedway in the city of Concord, North Carolina opposed this move, stating that it would cause excessive noise and traffic. The city of Concord then changed the zoning around the track, essentially preventing him from being able to build the drag strip. On October 2, 2007, Smith demanded that the Speedway and his surrounding land be unannexed from the city of Concord or he would shut down the speedway, taking hundreds of millions of dollars away from Concord and businesses surrounding it, and move it to a different plot of land within the metropolitan area of Charlotte, North Carolina. He said that he would be able to finish such a project with $350 million and 11 months.

On November 26, 2007, Smith announced his intent to retain Charlotte Motor Speedway in its current location in Concord. His decision was an apparent response to an incentive package offered by the city, county, and state, worth approximately $80 million. As part of the incentives, Speedway Boulevard was renamed to Bruton Smith Boulevard, and will be re-aligned or widened. The package includes three other major road projects near the speedway. Sources of funding for the projects are still under discussion, but could include a sales tax increase for local residents.

Smith announced that he would return the Labor Day weekend NASCAR race from Auto Club Speedway in California (where it had been run since 2004) to the south beginning in 2009. His Atlanta track hosted the late summer holiday weekend event from 2009 until its final running on August 31, 2014. Beginning in 2015 the race returns to its longtime Labor Day home in Darlington, S.C., a track not owned by Smith’s Speedway Motorsports, Inc. SMI’s Atlanta Motor Speedway will host its only race of 2015 on March 1.