Sports car racing at the top level in North America was fragmented for over a decade, split between the technology-focused American Le Mans Series and the cost-conscious Rolex Sports Car Series run by Grand-Am Road Racing. On 5 September 2012, Grand-Am and IMSA announced a merger of their sanctioning bodies and their premier series, with a planned debut in 2014. The merger committee selected SME Branding to develop the new series identity. A preliminary class structure was announced on 8 January 2013: Grand-Am's Daytona Prototype category and IMSA's P2 class would merge into a single prototype division, with the Nissan DeltaWing also permitted. The American Le Mans Series GT class would carry over unchanged, while Grand-Am's GT class would combine with the ALMS GTC category into a second GT division. The ALMS P1 class had no counterpart and was not carried forward.
The series was publicly unveiled on 14 March 2013 at the Chateau Élan Hotel and Conference Center at Sebring International Raceway, two days before the 12 Hours of Sebring. IMSA was confirmed as the continuing sanctioning body. The United SportsCar Racing title was submitted through a public naming contest and won by Louis Satterlee of Florida. Fox Sports 1 signed a television deal on 9 August 2013 to cover the entire USCC season from 2014 to 2018. Tudor was announced as title sponsor on 12 September 2013, naming the series the United SportsCar Championship for its first two seasons.
WeatherTech was named the new title sponsor on 8 August 2015, and the series has competed as the IMSA WeatherTech SportsCar Championship from the 2016 season onward. From 2019 NBC Sports became the series' exclusive US broadcaster, with nine hours of annual coverage on the NBC broadcast network, supplemental content on NBCSN and the NBC Sports app. USA Network replaced NBCSN as the cable home from 2022.
The season opens with the Rolex 24 at Daytona in late January and concludes with the Petit Le Mans at Road Atlanta in early October.
The IMSA Michelin Endurance Cup is an overlaid championship for drivers, teams, and manufacturers across five designated endurance events: the 24 Hours of Daytona, the 12 Hours of Sebring, the 6 Hours of Watkins Glen, the SportsCar Endurance Grand Prix, and the Petit Le Mans. The Endurance Cup began in 2014 as the Tequila Patrón North American Endurance Cup; Michelin assumed title sponsorship in 2019. Points are awarded at staggered intervals during each race, varying by race length.
The Grand Touring Prototype (GTP) class is the flagship division since 2023, replacing the Daytona Prototype International class. GTP cars are built to a dual homologation covering IMSA's LMDh regulations and the Automobile Club de l'Ouest's Le Mans Hypercar rules, aligning IMSA more closely with the FIA World Endurance Championship.
Le Mans Prototype 2 (LMP2) was split from the prototype class in 2019 and features pro-am driver lineups. Cars must be built by one of four ACO-licensed manufacturers — Riley-Multimatic, Ligier, Oreca, or Dallara — to the FIA/ACO 2017 Global LMP2 regulations.
The GT Daytona Pro (GTD Pro) class, introduced for 2022 as replacement for the GT Le Mans category, runs FIA GT3-specification machinery with no driver rating restrictions. GT Daytona (GTD) also uses GT3 cars but requires at least one silver- or bronze-rated driver per entry, and prohibits more than one platinum-rated driver per team.
Former classes include the Prototype Challenge (PC), a one-make class from 2014 to 2017 using Oreca FLM09 cars powered by 6.2-litre Chevrolet V8 engines producing 430 horsepower; LMP3, introduced in 2021 and removed after 2023 due to grid growth; and GT Le Mans (GTLM), which ran ACO GTE-specification cars from 2014 through 2021.
Driver entry to LMP2 and GTD is regulated by the FIA driver rating system: LMP2 teams may carry only one gold-rated driver per car, while GTD entries may not carry more than one platinum driver.
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