Since 1916 there has been a recognized United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 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

Indianapolis 500

The Indianapolis 500-Mile Race, also known as the Indianapolis 500, the 500 Miles at Indianapolis, the Indy 500 or The 500, is an American automobile race, held annually, typically on the last weekend in May at the Indianapolis Motor Speedway in Speedway, Indiana...

-mile race has been regarded as the marquee event of the National Championship. As of 2011

2011 IndyCar Series season

The 2011 Izod IndyCar Series season was the 100th season of American open wheel motor racing. The season consisted of seventeen events over the course of a seven–month season. Its premier event was the 95th Indianapolis 500, run on Sunday, May 29. It was the final season running the IR–05 Dallara...

, the top-level American open wheel racing championship is sanctioned by IndyCar

IndyCar

IndyCar is the trade name of an American-based open-wheel auto racing sanctioning body. IndyCar sanctions three racing series, the premier IZOD IndyCar Series with its centerpiece Indianapolis 500, and developmental series Firestone Indy Lights and the U.S...

.

The open-wheeled, winged, single-seater cars have generally been similar to those in Formula One

Formula One

Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...

, though there are important differences.