Nalon began his involvement in racing as a pit crew member for Wally Zale. He occasionally warmed up the race car, and when Walter Galven needed a driver, Zale persuaded Galven to give Nalon a chance behind the wheel. Nalon won the feature event on his first opportunity, establishing the trajectory of a long racing career.
Nalon won races in midget car competition on the United States East Coast during the 1930s and remained active in midget racing throughout his career. He won the 1938 East Coast AAA Sprint car championship, and won the Midwestern sprint car championship in 1941. His final career race was the only 100-mile midget race ever held at Terre Haute, where he drove Johnny Pawl's famous midget to victory — ending his career as he had begun it, with a win.
Nalon started ten Indianapolis 500-mile races, though he finished only three of them. He qualified on pole position twice and was twice the fastest qualifier at the Speedway, demonstrating exceptional one-lap pace even when race results did not reflect it.
His 1947 appearance was notable for his choice of machinery: he competed in a pre-war Mercedes-Benz W154 Grand Prix car, a relic of the dominant German teams from the late 1930s that found a brief second life on American ovals.
In 1949, Nalon was involved in one of the most dramatic and dangerous incidents in Indianapolis history. He backed into the wall, and his car erupted in flames. He survived by holding his breath to prevent asphyxiation and jumping clear of the burning car while it was still in motion. He sustained severe burns to his legs, injuries that troubled him for the remainder of his life until his death in 2001.
The Indianapolis 500 was included in the FIA World Drivers' Championship from 1950 through 1960, meaning drivers who competed at Indianapolis during those years were credited with World Championship participation alongside their AAA and USAC National Championship results. Nalon participated in three World Drivers' Championship races at Indianapolis. His best finish was tenth place, and he qualified on pole position once during those years. He did not score World Drivers' Championship points.
Nalon was inducted into the National Midget Auto Racing Hall of Fame in 1987, the National Sprint Car Hall of Fame in 1991, and the Motorsports Hall of Fame of America in 2015. These honours reflect his standing across multiple categories of American oval racing — midget, sprint, and championship Indy car — over a career that stretched from the 1930s through the early 1950s.
Duke Nalon died on 26 February 2001.