1990s, which saw the debuts of drivers from Europe, South America, and Japan, many of whom had previously competed in Formula One. This led to Tony George forming the IRL in order to promote American drivers. Conversely, American drivers have not found much success in Formula One since the 1970s; the last American driver to date to have won a Formula One race or the World Drivers' Championship was Mario Andretti, who accomplished both in 1978. Andretti was born in Italy in later became an American citizen. Due partly to the lack of American drivers and teams, Formula One struggled to establish itself in that market, with the United States Grand Prix not being part of the Formula One season in some years. In a parallel, Indy car racing has made little headway outside of the United States and Canada, despite occasionally having races overseas. Types of circuits The American National Championship is notable for the wide variety of racetracks it has used compared to other series, such as Formula One and the various forms of Endurance sports car racing. The mainstays of the championship are as follows: Paved ovals and tri-ovals (e.g. Indianapolis, Texas) Permanent (or "Natural") road courses (e.g. Barber, Mid-Ohio) Temporary street circuits/courses (e.g. Long Beach, St. Pete) Combined road course (e.g. IndyCar Grand Prix) Until 1970 the championship frequently raced on dirt and clay tracks, but all such tracks were removed permanently by USAC before the 1971 season. From 1915 to 1931 board tracks were frequently used for championship races, however safety concerns and cost of maintenance, especially with the onset of the Great Depression, and nearly all were demolished in the 1930s. The Pikes Peak Hillclimb was a round of the championship in the years 1947—1955 and 1965–1969. In 1909 a point-to-point race from Los Angeles to Phoenix was included in the championship. Airport runways have also been used to create temporary circuits. The most notable used for open-wheel racing was the Cleveland Grand Prix at Burke Lakefront Airport. St. Pete and Edmonton also utilize airport runways for parts of the course, however, they lead back to streets for the rest of the lap. Events outside the United States For the majority of the national championship, the races have been held inside the United States. American championship cars raced at the Monza oval in 1957 and 1958 alongside Formula One and sports cars in the