American open wheel races

Since 1916 there has been a recognized United States national automobile racing National Championship for drivers of professional-level, single-seat open wheel race cars. The championship has been under the auspices of several different sanctioning bodies since 1909. Since 1911, the Indianapolis 500-mile race has been regarded as the marquee event of the National Championship. As of 2008, the top-level American open wheel racing championship is sanctioned by the Indy Racing League.

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- Race cars participating in national championship events have been referred to by various names. Early nomenclature was to call the machines "Championship Cars," which was later shortened to "Champ Cars." The ambiguous term "Big Cars" was also commonplace in early years.