Competitive events for professional-level, open-wheel race cars have been conducted under the auspices of various sanctioning bodies, tracing its roots as far back as 1902.

A season-long, points-based, National Championship of drivers has been officially recognized in 1905, 1916, and each year since 1920 (except for a hiatus during WWII).

Though the IndyCar Series is U.S.-based, international races have occasionally been held; in such places as Canada, Mexico, Brazil, Japan, Australia, as well as Europe.

It cited a series of high-profile fatal accidents, namely Bill Vukovich during the 1955 Indianapolis 500, and the 1955 Le Mans disaster.

The national championship was taken over by the United States Auto Club (USAC), a new sanctioning body formed by the then-owner of the Indianapolis Motor Speedway, Tony Hulman.

In the 1960s, drivers and team owners with road racing backgrounds, both American and foreign, began creeping into the series and the paved oval track cars evolved from front-engine "roadsters" to rear-engine formula-style racers.

The schedule continued to be dominated by oval tracks, but a few road course races were added to assuage the newcomers.

The dominant teams became Penske, Patrick, Gurney, and McLaren, all run by people with road racing backgrounds.

Towards the end of the decade, the growing dissent prompted several car owners to consider creating a new sanctioning body to conduct the races.

[7] Both CART and USAC awarded separate national championship titles that year, and Johnny Rutherford happened to win both.

This race was not supported by many CART teams, and featured a mixed field filled out by converted dirt track cars.

On occasion, some of the "Indy only" entries also elected to participate in the Michigan 500 and Pocono 500 (both sanctioned by CART) given the increased stature and exposure of those two events.

One of the more noticeable rule differences by USAC was allowing "stock block" engines a higher level of turbocharger boost.

CART's existing national championship remained dominant after the split for some time, initially retaining the top drivers, teams, and sponsors.

After steadily losing teams and drivers, sponsors, and manufacturers, and after a series of major financial setbacks, CART filed for bankruptcy in 2003.

However, the sanctioning body continued to be plagued by financial difficulties, In 2007, CCWS's presenting sponsors Bridgestone and Ford Motor Company withdrew.

During this time, the IRL was now operating under the moniker IndyCar Series, and slowly beginning to establish itself as the more preeminent national championship trail.

Prior to the start of the 2008 season, the CCWS Board authorized bankruptcy and Champ Car was absorbed into the IRL, creating a unified series for the national championship for the first time since 1978.

The two calendars were merged into one schedule, with the top Champ Car races such as Long Beach (which was a CCWS-sanctioned event with IRL points before being an official round of the IRL in 2009), Edmonton and Surfers Paradise in Australia surviving, later being replaced with an A1GP event in 2009 that never happened before the focus was changed to the Australian Supercars Championship in 2010.

[11] In 2011, the sanctioning body dropped the Indy Racing League name, becoming IndyCar to reflect the merged series.

In the 1960s, road racing gained popularity in North America, and Formula One-style design ideas changed IndyCars, which until then had all been classic-styled front-engined roadsters.

When North America's road racing championship, Can-Am Challenge, collapsed in the 1970s, the IndyCars were ready to fill the void.

Compared to F1 cars, IndyCars were partly specialized for oval-racing: they were larger and had other safety features,[citation needed] and were designed to run at the higher speeds necessary for oval racing.

After the Split in the 1990s, CART maintained the old formula while the IRL drifted toward the "spec" design that has been the only IndyCar model since 2003 (which changed in 2012, with specialized aero kits available from 2015 to 2017).

A handful of notable IndyCar drivers, however, found subsequent success in F1, including Mario Andretti and Jacques Villeneuve, who became Formula One champions, and Juan Pablo Montoya, who won several F1 races.

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.

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.

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.

In the 1990s and early 2000s, international expansion reached overseas with events at Surfer's Paradise, Rio de Janeiro, Motegi, Lausitz, and Rockingham.

A black granite base has been added displaying the names of all the American Championship car racing series winners since 1909.