John Bishop, a Sikorsky employee, first became involved in motorsport in the 1950s when he met Dave Allen, an SCCA staff member, who offered him a management position on the SCCA Contest Board. Bishop moved to Westport, Connecticut, and his duties included defining technical rules and general administration of SCCA competition. He enjoyed a good relationship with the organization's president, James H. Kimberly. In 1958 the SCCA created a new executive director position taken by Hugo Rush; though Bishop's relationship with Rush was poor, he gained experience as a manager. Rush later departed over disagreements as the club moved toward professional motor sports, and Bishop took his place as executive director.
By 1962 the SCCA was managing major World Championship for Makes rounds at Daytona, Sebring, Bridgehampton, and Watkins Glen, and was involved in the United States Grand Prix. Bishop helped create the USRRC (United States Road Racing Championship) for Group 7 sports cars and was instrumental in founding both the SCCA Trans-Am series and the SCCA/CASC Can–Am series. In 1969, internal tension and infighting caused Bishop to resign.
Bill France Sr. wanted to create a professional road racing series complementing NASCAR's oval focus. After discussions with Bishop, IMSA was incorporated in Connecticut on June 23, 1969. France financed the majority of the organization and owned 75 percent of the stock; Bishop owned the remaining 25 percent.
The first race organized by IMSA was a Formula Vee and Formula Ford event at Pocono Raceway in October 1969. The SCCA threatened circuit management and asked them to block IMSA from racing there; the event proceeded, but IMSA had to pay an additional $10,000 in rental fees. Attendance reached 328 spectators. Bill France, facing financial setbacks, subsequently brought in new investors to take over part of his stake.
At the end of the 1970 season, Bishop helped establish the FIA "J appendix" for World Championship for Makes sports cars. The 1971 Grand Touring (GT) season introduced international endurance racing to North America. In 1972, Camel Cigarettes became the new series sponsor, and the sedan series became known as the BFGoodrich Radial Challenge. The 12 Hours of Sebring joined the IMSA GT Championship schedule in 1973, the same year IMSA gained recognition from ACCUS and the FIA. IMSA was scheduled to sanction the 1974 24 Hours of Daytona, but that race was cancelled due to the oil crisis.
Bishop prioritized privateer teams and tried to ensure rules were not biased in favor of factory entries. As European cars began to dominate, a new series called All American Grand Touring (AAGT) was formed in 1975. Turbocharged cars were permitted from 1977. A pair of Jean Rondeau-built Inaltera prototypes, invited to compete as "special prototypes," became the foundation of the newly formed Grand Touring Prototype (GTP) category in 1981, with separate rules similar to Group C.
In 1984, FISA — organizers of the World Endurance Championship — attempted to unite the two organizations by adopting IMSA rules, a move opposed by Porsche, which was spending heavily on engine development. Porsche boycotted the 24 Hours of Le Mans that year in response. FISA abandoned the rule change. In 1987, FISA president Jean-Marie Balestre nearly settled the dispute by announcing turbochargers and fuel restrictions would be phased out by 1989; this attempt also failed, as did another in 1991.
In 1987 John Bishop underwent coronary artery bypass surgery, prompting him to reconsider his priorities. Concerned the Camel GT series was drifting toward factory teams and away from its privateer roots, he sold the company to Mike Cone and Jeff Parker in January 1989. Bishop stepped down as president in favor of his deputy, Mark Raffauf. Cone and Parker sold the organization to businessman Charles Slater by the early 1990s. In 1996 Slater sold the organization — carrying accumulated debt — to Roberto Muller (ex-CEO of Reebok) and Andy Evans, a Wall Street portfolio manager for Bill Gates, IndyCar owner, and owner-driver of the Scandia World Sports Car team. These changes led to the departure of many executive board members. Evans was responsible for renaming the organization to Professional Sports Car Racing (PSCR).
In 1998 the United States Road Racing Championship was revived as an alternative to PSCR, involving the SCCA and headed by a group of competitors and ex-IMSA personnel including John Bishop, Bill France Jr., Rob Dyson, Roger Penske, Skip Barber, and Ralph Sanchez. When this effort initially failed, Don Panoz and Barber affiliated themselves with PSCR.
In spring 1998, Don Panoz created a partnership with the Automobile Club de l'Ouest (ACO), organizers of the 24 Hours of Le Mans, to run a 10-hour race in the spirit of Le Mans called the Petit Le Mans, held at Panoz's Road Atlanta facility. Following the inaugural Petit Le Mans' success as part of the 1998 IMSA GT Championship, Panoz announced the American Le Mans Series (ALMS) for 1999, adopting the ACO's rulebook under PSCR sanction.
Under pressure from team owners, Evans sold Professional Sports Car Racing to Don Panoz in 2001 to consolidate the ALMS. Panoz renamed the sanctioning body back to the International Motor Sports Association. IMSA became part of Panoz Motorsports Group, which included the ALMS, Elan Motorsports Technology, and the Mosport, Sebring, and Road Atlanta race tracks. Scott Atherton was appointed President of Panoz Motorsports Group. IMSA's main series, the ALMS, focused on manufacturer entries and top privateers, increasing the championship's worldwide prestige.
A second sports car sanction body, Grand-Am Road Racing, was created with full support of the France family and debuted in 2000. Grand-Am's philosophy centered on lower-tech cars, most notably the Daytona Prototype, delivering larger fields and closer racing. This split was widely seen as detrimental to the sport as a whole, drawing comparison to the Champ Car/IRL divide.
In 2012 Don Panoz sold the Braselton, Georgia-based ALMS to Grand-Am Road Racing, itself owned by NASCAR, facilitating a merger with the Rolex Sports Car Series. In 2013 the unified series was announced as the Tudor United SportsCar Championship (now IMSA SportsCar Championship), managed by IMSA as a wholly owned subsidiary of NASCAR. The series debuted on January 25–26, 2014 at Daytona International Speedway. For the 2016 season, title sponsorship changed from Tudor to WeatherTech.
Scott Atherton announced retirement from the presidency of IMSA on September 19, 2019. John Doonan, then-director of Mazda's motorsports program in North America, was confirmed as Atherton's replacement. Ed Bennett, longtime NASCAR executive, served as President and CEO of Grand-Am Road Racing from August 2011 to December 2013 during the merger period and has continued as CEO of the modern IMSA since January 2014.
At the 2021 Daytona 24 Hours, IMSA and the ACO announced historic alignment of technical regulations for sportscar racing, further detailed in June 2021, converging all sportscar regulations between the FIA, IMSA, and the ACO. In January 2022, IMSA acquired Historic Sportscar Racing, whose events include the Classic 24 Hours of Daytona, the Classic 12 Hours of Sebring, and the Monterey Motorsports Reunion.
The IMSA WeatherTech SportsCar Championship is the premier series, currently featuring LMDh, LMP2, and GT3 cars. The IMSA Michelin Pilot Challenge is a grand touring and touring car racing series using TCR Touring Cars and GT4 cars; Continental Tire was title sponsor from 2010 until 2018, replaced by Michelin in 2019. The IMSA VP Racing SportsCar Challenge, introduced in 2023, is a development series featuring LMP3 and GT4 cars in two 45-minute sprint races, requiring Silver or Bronze FIA driver categorization.
Manufacturer-specific series include the Porsche Carrera Cup North America (a Porsche 911 GT3 one-make series held since 2005), the Ferrari Challenge (dedicated to the Ferrari 296 Challenge), the Lamborghini Super Trofeo North America (dedicated to the Lamborghini Huracán LP 620-2 Super Trofeo EVO2, debuting in North America in 2013), the Mazda MX-5 Cup (cars built at Mazda's Hiroshima factory and prepared by Flis Performance in Daytona Beach, under IMSA sanction since 2021), and the Ford Mustang Challenge (announced July 27, 2023, for the 7th Generation Mustang organized with Ford Performance Racing School). The IMSA HSR Prototype Challenge was announced October 24, 2023, as a prototype-only series for LMP3 Gen 1 and Gen 2 cars within Historic Sportscar Racing events.
The IMSA RS Series (for radial sedan), beginning as the Baby Grand Series in 1971, featured production-based sedans and was sponsored successively by BFGoodrich, Goodyear, and Champion Spark Plug. The series was dominated by Mazda's rotary-powered RX-2 and RX-3, with Datsun also achieving success with the 510 and 200SX. Notable drivers who came through the series include Bobby Rahal. The series ran until 1984 before being replaced by the IMSA Showroom Stock class.
The American Challenge (Kelly American Challenge) ran from 1977 to 1989 as a support race to the premier GT series for US-built cars. It launched the careers of Kenny Irwin Jr., Patty Moise, and Lyn St. James.
The IMSA Renault Cup, a one-make series running between 1982 and 1985, was conceived by the Associated Road Racers (ARR) founded by Steve Coleman of Raleigh, North Carolina. The inaugural race at Road Atlanta on April 4, 1982 drew 51 Le Car entries. Notable alumni include Parker Johnstone.
The IMSA Showroom Stock series replaced the RS Series in 1985 and ran until 1998. From 1988 it was known as the IMSA Firestone Firehawk Endurance Championship. Professional drivers including Dorsey Schroeder and John Andretti competed, and meetings regularly drew over ninety entries.
The IMSA Bridgestone Supercar Championship ran from 1991 to 1995 for high-end sports cars including the Porsche 911 Turbo, Lotus Esprit X180R, Chevrolet Corvette, Mazda RX-7, and Nissan 300ZX. It attracted drivers such as Hans-Joachim Stuck, Hurley Haywood, Doc Bundy, and Paul Newman. The controversial all-composite Consulier GTP debuted with four cars at Lime Rock in 1991 and was subsequently excluded by end of season after receiving a 300 lb weight penalty.
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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