The national championship was sanctioned by the Contest Board of the American Automobile Association (AAA), which first sanctioned motorsport events in 1902 and introduced the first track season championship in 1905, with Barney Oldfield as the first champion. No official season championship was recognised from 1906 to 1915; retroactive titles covering those years are considered unofficial by accredited historians. The championship officially resumed in 1920 and ran continuously through the Depression. All auto racing was suspended from 1942 to 1945 by the U.S. government on account of wartime rationing; the Indianapolis 500 itself was voluntarily suspended for 1917–1918 and 1942–1945. Through 1922 and again from 1930 to 1937, it was commonplace for cars to carry a riding mechanic alongside the driver. AAA ceased involvement in auto racing at the end of 1955, citing high-profile fatal accidents including Bill Vukovich during the 1955 Indianapolis 500 and the 1955 Le Mans disaster.
The United States Auto Club (USAC) took over the national championship, formed by Indianapolis Motor Speedway owner Tony Hulman. During the 1950s, front-engined roadsters dominated paved oval tracks while upright Champ Dirt Cars dominated on dirt. In the 1960s, drivers and teams with road racing backgrounds — both American and foreign — entered the series, and cars evolved from front-engined roadsters to rear-engined formula-style machines. Dirt tracks were dropped from the national championship after 1970. Teams including Team Lotus, McLaren, Team Penske, and All American Racers competed and won in both Formula One and USAC events during the 1960s and 1970s.
Increasing costs through the 1970s drove some traditional USAC car owners from the sport. The dominant teams — Penske, Patrick, Gurney, and McLaren — all had road racing backgrounds and grew dissatisfied with USAC management. Hulman died in autumn 1977, and a few months later eight key USAC officials were killed in a plane crash. By the end of 1978, owners had founded Championship Auto Racing Teams (CART) to take control of North American single-seater championship racing away from USAC.
CART was formed by most existing team owners, and two separate national championships were run concurrently by USAC and CART. The Indianapolis 500 remained under USAC sanction while the top teams aligned with CART, whose championship quickly became the more prestigious. In 1979, USAC denied several CART team entries at the Indianapolis 500; a court injunction during the month allowed the CART-affiliated entrants to participate. In 1980, USAC and CART jointly formed the Championship Racing League (CRL), but IMS management disapproved and USAC withdrew in July; both bodies awarded separate national championship titles that year, with Johnny Rutherford winning both. By 1981–1982, USAC ceased sanctioning championship races outside the Indianapolis 500.
CART ran the national championship full-time from 1982. The Indianapolis 500, sanctioned by USAC, paid championship points towards the CART season title. The USAC Gold Crown Championship, which continued as a separate entity, settled into an unusual June-through-May calendar; between 1984–85 and 1994–95 it consisted solely of the Indianapolis 500, making the Indy 500 winner the USAC Gold Crown champion by default.
In 1994, Tony Hulman's grandson Tony George, president of the Indianapolis Motor Speedway, founded the Indy Racing League (IRL) to begin competition in 1996. The IRL guaranteed automatic Indianapolis 500 qualification to 25 teams that competed in IRL races, making it effectively impossible for most CART teams to qualify. CART teams boycotted the 1996 Indianapolis 500 — the beginning of the second split. USAC initially sanctioned the IRL, but after officiating controversies in 1997 was replaced by the IRL's in-house officials. CART entered a legal battle with the Indianapolis Motor Speedway over the trademarked "IndyCar" name; as part of a settlement, CART relinquished the name and rebranded its machines as Champ Cars. CART initially retained the top drivers, teams, and sponsors after the split, but from 2000 teams began returning to the Indianapolis 500 and eventually defecting to the IRL. For 2003, CART lost title sponsor FedEx and engine manufacturers Honda and Toyota to the IRL.
CART filed for bankruptcy in 2003. Its assets were purchased by Open Wheel Racing Series (OWRS) in 2004, which renamed the series the Champ Car World Series (CCWS). CCWS continued to face financial difficulties; in 2007 presenting sponsors Bridgestone and Ford Motor Company withdrew. The IRL, operating as the IndyCar Series, gradually established itself as the more prominent championship, adding road and street courses from 2005. In 2007, Champ Car raced in Europe for the first time since 2003, at circuits in the Netherlands and Belgium; the 2007 Champ Car schedule — its last — was the only season in the combined history of all major American open-wheel series not to feature any oval races.
Prior to the 2008 season, the CCWS board authorised bankruptcy and Champ Car was absorbed into the IRL, creating a unified series for the first time since 1978. The merged calendar incorporated top Champ Car rounds including Long Beach, Edmonton, and Surfers Paradise. The Indy Racing League name was retired on 1 January 2011; the sanctioning body became INDYCAR LLC and the premier series was named the IndyCar Series. The new Dallara DW12 chassis was introduced for the 2012 season. The series was known as the IZOD IndyCar Series from 2010 to 2013, the Verizon IndyCar Series from 2014 to 2018, and the NTT IndyCar Series from 2019.
In 2020, the IndyCar Series, Indianapolis Motor Speedway, and associated holdings were sold to Penske Entertainment Corp., a subsidiary of Penske Corporation owned by Roger Penske.
A.J. Foyt holds the most championship titles and race wins — 67 USAC championship race wins and seven USAC titles between 1959 and 1981. Mario Andretti is the most successful driver born outside the United States, with 52 total wins (33 USAC and 19 CART) and four titles. New Zealand's Scott Dixon is the most successful non-U.S. driver with six championship titles and 50 race wins (including one CART win in 2001). Michael Andretti won the most CART/Champ Car-sanctioned races (42). Tony Bettenhausen holds the most AAA championship race wins (19). Danica Patrick is the only woman to win a national championship-level open-wheel race, at Motegi in 2008; Sarah Fisher was the first woman to win a pole position, at Kentucky in 2002. Four drivers have held both the CART champion title and the Formula One World Drivers' Championship: Emerson Fittipaldi, Nigel Mansell, Mario Andretti, and Jacques Villeneuve. Several others won both a national championship race and at least one Formula One Grand Prix, including Juan Pablo Montoya, Jackie Stewart, Dan Gurney, Jim Clark, Graham Hill, and Peter Revson.
The American National Championship has used a wider variety of racetracks than most comparable series. Paved ovals and tri-ovals, permanent road courses, temporary street circuits, and combined road courses have all featured. Dirt and clay tracks were used until 1970; board tracks from 1915 to 1931 before safety concerns and Great Depression economics led to their demolition. The Pikes Peak Hillclimb was a championship round in 1947–1955 and 1965–1969. American championship cars raced at the Monza oval in 1957 and 1958 in the non-championship Race of Two Worlds alongside Formula One. The first championship events outside the United States were held at Mosport and Saint-Jovite in Canada in 1967.
Jimmy Murphy, champion in 1922 and 1924, died after crashing at the Syracuse Mile in September 1924. Ted Horn, champion in 1946, 1947, and 1948, died after crashing at the DuQuoin dirt track in late 1948. Tony Bettenhausen was killed in a crash at Indianapolis in May 1961. Eddie Sachs and Dave MacDonald were killed during the 1964 Indianapolis 500. Art Pollard and Swede Savage died from injuries suffered during the 1973 Indianapolis 500. Gordon Smiley was killed while attempting to qualify for the 1982 Indianapolis 500. Scott Brayton, the 1996 Indianapolis 500 pole-sitter, was killed in practice on 17 May 1996. Gonzalo Rodríguez was killed on 11 September 1999 during qualifying at Laguna Seca. Greg Moore died after a crash on 31 October 1999 in the Marlboro 500 at Fontana. Paul Dana died during practice at Homestead-Miami Speedway on 26 March 2006. Dan Wheldon, two-time Indianapolis 500 champion, died after a 15-car pile-up on the 11th lap of the 2011 IZOD IndyCar World Championships at Las Vegas Motor Speedway. Justin Wilson died on 24 August 2015 from injuries suffered in the 2015 ABC Supply 500 at Pocono Raceway.
The Astor Cup, first awarded in 1915, was revived by IndyCar in 2011 as the series championship trophy, with a black granite base displaying the names of all championship car racing series winners since 1909. The Vanderbilt Cup, whose races in 1909–1916 and 1936–1937 were included in the national championship, was resurrected by CART in 1996 as the winner's trophy for the US500, later serving as the championship trophy until Champ Car's merger with the IRL.
This article is based solely on the supplied corpus. No external sources were consulted; claims that could not be substantiated against the corpus were omitted under the drop-the-claim rule.
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