American open-wheel car racing, also known as Indy car racing, is a category of professional automobile racing in the United States. As of 2022, the top-level American open-wheel racing championship is sanctioned by IndyCar. Competitive events for professional-level, single-seat open-wheel race cars have been conducted under the auspices of various sanctioning bodies since 1902. A season-long, points-based, National Championship of drivers has been officially recognized in 1905, 1916, and since 1920. The open-wheeled, winged, single-seater cars have generally been similar to those in Formula One, though there are important differences. The cars that compete on the American Championship circuit are popularly known as "Indy cars" after the Indianapolis 500, the premier event of Indy car racing. This form of racing was especially popular in the decades after World War II. The "golden era" of the 1950s was followed by a decade of transition and innovation in the 1960s, which included increased international participation. The sport experienced considerable growth and exposure during the rising popularity of the CART PPG Indy Car World Series in the 1980s and early 1990s. Organizational disputes in 1979 and 1996 split participants (and fans) among two separate sanctioning bodies until the sport was re-unified in 2008. Sanctioning bodies AAA (1902–1955) The national championship was sanctioned by the Contest Board of the American Automobile Association (AAA). The AAA first sanctioned automobile motorsports events in 1902. At first it used the rules of the Automobile Club of America (ACA), but it formed its own rules in 1903. It introduced the first track season championship for racing cars in 1905. Barney Oldfield was the first champion. No official season championship was recognized from 1906 to 1915, however, many races were held. Official records regard 1916 as the next contested championship season. Years later, retroactive titles were named back to 1902. These post factum seasons (1902–1904, 1906–1915, and 1917–1919) are considered unofficial and revisionist history by accredited historians. Racing did not cease in the United States during WWI, but the official national championship was suspended. The Indianapolis 500 itself was voluntarily suspended for 1917–1918 due to the war. In 1920, the championship officially resumed, and despite the difficult economic climate that would later follow, ran continuously throughout the Depression. Shortly after Pearl Harbor, all auto racing was suspended during World War II. From 1942 to 1945 no events were contested, banned by the U.S. government primarily on account of rationing.