Frank Kurtis is the undisputed father of the Indy roadsters—to this day, among America’s most beloved race cars. Here’s a brief history. 

Years before he created the familiar Indy roadster, Frank Kurtis was already a popular and successful car builder at the Speedway and elsewhere. Cars from his Southern California shops dominated midget and championship racing in the postwar era, scoring victories in the Indianapolis 500 in 1950 and 1951. It was in 1952 that Kurtis introduced his most memorable and revolutionary idea—a low-slung race car design that proved to be as successful as it was beautiful.

Speedway historians say you can see the first stirrings of the roadster configuration in the Ross Page Special, constructed by Kurtis for the 1946 season (above). The engine and drivetrain are centered in this chassis, but the driver is offset to the left of the driveshaft, rather than perched on top, to lower the center of gravity and reduce frontal area.  However, it would take a few more years for the roadster concept to take full flower. Kurtis conceived many of his innovations years before they appeared on his race cars, reportedly. It seems he loved to innovate but was often frustrated by his conservative customers, who demanded exact copies of his most successful designs.

The 1952 Cummins Diesel Special, which Kurtis designed and built for the Cummins Diesel organization in Columbus, Indiana, is often cited as the first true roadster. To compensate for the massive height and weight of the ponderous 401 CID diesel engine, Kurtis leaned it over on its side, offsetting the drivetrain to the left and the cockpit to the right. Above, builder Kurtis (left), driver Freddie Agabashian, and a Cummins executive holding a yardstick admire the attractively low cowl height: a mere 23 inches  While too heavy and hard on its tires to be competitive for 500 miles, the Cummins won the pole convincingly in ’52, demonstrating the clear merit of the roadster layout.

Along with the Cummins Special in 1952, Kurtis also built a small batch of customer cars designed to accept conventional engines. In these chassis, the cockpit was offset and in one, Howard Keck’s Fuel Injection Special, the four-cylinder Offy engine was offset left and tipped 36 degrees. (Note the starter tube location in the front grille, a tell to the crankshaft location.) This proved to be the magic formula, as the Keck Kurtis dominated the Speedway in 1952 and then won going away in 1953 and 1954 with driver Bill Vukovich.  Kurtis and his California shop were flooded with orders (and imitators) and the roadster era at Indy was under way. In 1955, the top three finishers were driving Kurtis roadsters, and Kurtis chassis of various types made up nearly two-thirds of the field.

Throughout the roadster era at the Brickyard, Kurtis continued to refine and develop the the basic layout, experimenting with various engine offsets and inclinations. On this  Bardahl Special above, the Offy engine is offset to the right and inclined to the left, while the cockpit is offset left, the reverse of standard practice. Kurtis also tried out independent front suspension and restyled sheet metal (below).

If imitation is the sincerest form of flattery, the Kurtis roadster was admired indeed. The design inspired countless copies and spinoffs from Kuzma, Lesovksy, and others, but easily the most successful of the lot was the Watson, a lighter, simpler version of the Kurtis that won the Indianapolis 500 six times and generated its own string of copycats. The roadster era would endure at Indy until 1965, when the elegant dinosaurs were finally unseated by mid-engined cars.