Petty was born in Randleman, North Carolina. He made his major-league stock car debut at the age of 18. He won the very first race he entered, the 1979 Daytona ARCA 200, in one of his father's old 1978 Dodge Magnum race cars; at the time, Petty became the youngest driver to win a major-league stock car race. Later in the season, he made his Winston Cup Series debut; again driving a passed down STP Dodge Magnum numbered No. 42 (a number used by his grandfather Lee Petty) for his family's team. He ran five races and had a ninth-place finish in his first series race, the 1979 Talladega 500. In 1980, he made a total of fifteen starts in the No. 42 (after crashing the last of his father's Dodge Magnums in one of the Daytona 125 qualifying races) and had six top-ten finishes, garnering a twenty-eighth-place points finish. He began the 1981 season driving his father's No. 43 for one race, before running a full schedule in his regular No. 42, finishing in the top-ten ten times and finishing twelfth in points.