Walt Hansgen grew up to become a four-time SCCA Road Racing Champion, establishing himself as one of the most consistently successful American sports car competitors of his era. He drove primarily for Briggs Cunningham's team in the late 1950s and early 1960s, but also entered his own efforts and later drove for John Mecom's operation. Hansgen was respected not only for his speed but for his influence on younger talent — he was credited with introducing Mark Donohue to professional road racing.
Hansgen won races at Virginia International Raceway, Bridgehampton, and Watkins Glen across a career spanning from the early 1950s until his death. He drove for Cunningham at the 1960 24 Hours of Le Mans in a Jaguar E-Type alongside Dan Gurney, though the car retired with engine trouble.
In Formula One, Hansgen made his Grand Prix debut on October 8, 1961, at Watkins Glen, driving a Cooper T53 entered by the Momo Corporation, an organization associated with Cunningham's team. The car crashed on lap 14, marking the only F1 start of Hansgen's career. He scored a total of two World Championship points across his two Formula One appearances. The Cooper chassis from his debut was subsequently sold to Roger Penske, becoming the Zerex Special, and was later resold to Bruce McLaren as the first car of the McLaren racing team.
Hansgen also pursued single-seater racing in the United States. At the 1964 Indianapolis 500 he drove the MG Liquid Suspension Special, an Offenhauser-powered car entered by Kjell Qvale, finishing thirteenth. He returned to Indianapolis in 1965 in the MG-Huffaker-Offenhauser, finishing fourteenth.
On October 17, 1965, Hansgen won the Monterey Grand Prix at Laguna Seca Raceway driving John Mecom's Lola T70-Ford. He also won the Formula Junior race at the inaugural United States Grand Prix meeting held at Sebring on December 12, 1959, driving a Stanguellini.
Hansgen was killed as a result of an accident during wet-weather testing at Le Mans on April 3, 1966. He was driving a 7-litre Holman and Moody Ford GT40 Mk2 when the car appeared to aquaplane on the rain-soaked circuit. Team manager Carroll Smith had warned Hansgen to exercise caution in the conditions. According to Mark Donohue's account, Hansgen attempted to take an escape road only to find a barrier had been erected across it for spectator safety. He died from his injuries on April 7, 1966, aged 46.
Walt Hansgen's combination of consistent SCCA dominance — four national road racing championships — and ambitious forays into Formula One and Indianapolis made him one of the most complete American road racers of his generation. His mentorship of Mark Donohue, who went on to become one of the most successful American drivers of the following decade, stands as a lasting contribution to the sport beyond his own results on track.