He began his career helping Wally Zale in the pits. Zale allowed Duke to warm the car up on occasion. He entered his first race in 1935, when the driver for Walter Galven's Model T sprint car failed to show at Roby Speedway in northwest Indiana. Zale talked Galven into giving Nalon the drive. After winning the 50-lap feature race on the 1-mile dirt oval and the $55 prize, Nalon promptly quit his job at a steel mill to become a professional race driver.
He entered 10 Indy 500's, winning pole position in 1949 and 1951 (driving the Novi), and finishing 3rd in 1948. He first raced at Indy in 1937, trying to qualify an Elgin Piston Pit Special, but failed. The Chicago native became a big winner on the East Coast in midgets in the mid-thirties and also drove the big cars.
In 1938 he captured the East Coast AAA Sprint Car Championship and also drove in his first Indianapolis 500 starting 33rd and finishing 11th. World War II intervened, and he returned, racing at Indy and racing midgets. He miraculously survived a fiery crash that resulted from a broken rear axle while he was leading early in the 1949 Indy 500.
Nalon was a part of the famous Chicago Gang and teamed with a youthful Tony Bettenhausen when he was starting his career. Duke raced for a living and took care of his equipment while running up front. He competed in the midgets throughout his career.
In 1954 he drove Johnny Pawl's famous midget to victory in the only 100 mile midget race ever run at Terre Haute. It was a fitting end to a great career, having won his first and last start. He got his nickname "Duke" form his brother Charles, who called him "Duke McGluke from the hi-dry and windy" to distinguish him from their older brother Danny.