IMSA. 2026 season

Origin

The International Motor Sports Association was incorporated in Connecticut on 23 June 1969 by John Bishop — a former executive director of the Sports Car Club of America — and his wife Peggy, financed by NASCAR founder Bill France Sr., who held 75 per cent of the stock to Bishop's 25.¹² The first IMSA-sanctioned event was a Formula Vee and Formula Ford meeting at Pocono in October 1969, but Bishop abandoned open-wheel plans within a year and built a six-race GT series for 1971 instead.² R.J. Reynolds' Camel sponsorship arrived in 1972, the Sebring 12 Hours joined the schedule in 1973, and the Camel GT became the centre of professional sports car racing in North America — run, unusually, as a family business: Peggy Bishop managed registration, timing, and scoring throughout.²³

Turning points

The GTP era and the long decline

Bishop introduced the GTP prototype category in 1981, and the decade it defined — Porsche 962s against works Jaguars, Nissans, and Toyotas — remains the benchmark American sports car era.² Bishop, rethinking his priorities after heart surgery, sold the company to Mike Cone and Jeff Parker in January 1989; ownership churned through the 1990s as manufacturer budgets inflated and left, GTP collapsed after 1993, and the organisation was even renamed Professional SportsCar Racing in 1997.¹²

The split

In 1998 Don Panoz staged Petit Le Mans at Road Atlanta under a partnership with the Automobile Club de l'Ouest, then launched the American Le Mans Series for 1999 on the ACO rulebook — a direct pipeline between American racing and Le Mans.² Jim France answered with Grand-Am Road Racing, which debuted at the 2000 Rolex 24 at Daytona and from 2003 ran its own deliberately cheap Daytona Prototype formula.² For fourteen seasons North America carried two rival sports car championships with incompatible cars, split manufacturer money, and divided fields — a schism the sport could not afford indefinitely.⁴

The merger

France and Panoz announced the merger at Daytona in September 2012: Grand-Am absorbed the ALMS, the combined series debuted at the 2014 Rolex 24, and the IMSA name was retained as sanctioning body — the TUDOR United SportsCar Championship, renamed the WeatherTech SportsCar Championship in 2016.⁴¹ The decisive structural move came in 2023, when IMSA's revived GTP class adopted the LMDh hybrid-prototype ruleset developed jointly with the ACO, making cars eligible for both the WeatherTech Championship and the World Endurance Championship — Porsche, Cadillac, Acura, and BMW launched the class, and the Rolex 24 and Sebring returned to being global-calendar fixtures rather than domestic ones.⁵⁶

Today's shape

Porsche Penske Motorsport swept the 2025 GTP drivers', teams', and manufacturers' titles for the second consecutive season — Matt Campbell and Mathieu Jaminet clinched the drivers' crown with third place at Petit Le Mans, Roger Penske's fifteenth sports car championship — while the No. 31 Cadillac of Jack Aitken, Earl Bamber, and Frederik Vesti won the race itself.⁷ At the 2026 Rolex 24, Felipe Nasr took a record-tying third consecutive overall win — joining Hélio Castroneves and Peter Gregg — sharing the No. 7 Porsche 963 with Julien Andlauer and Laurin Heinrich, 1.5 seconds clear of the No. 31 Cadillac after a race interrupted by a record six-and-a-half-hour fog caution.⁸ The 2026 championship fields 45 full-season entries across four classes — 11 GTP, 12 LMP2, 8 GTD Pro, 14 GTD — growing to 54 cars for the five Michelin Endurance Cup rounds; Acura, BMW, Cadillac, and Porsche have all introduced Evo updates of their GTP hybrids, BMW's programme moved to Team WRT, and Aston Martin's Valkyrie remains the only Le Mans Hypercar in the field.⁹⁶

Footnotes

1. Wikipedia, "IMSA," accessed 11 June 2026, https://en.wikipedia.org/wiki/IMSA. ↩ ↩² ↩³

2. IMSA Hall of Fame, "Timeline," accessed 11 June 2026, https://www.imsahalloffame.com/timeline/. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

3. IMSA Hall of Fame, "John Bishop and Peggy Bishop," accessed 11 June 2026, https://www.imsahalloffame.com/drivers/john-bishop/. ↩

4. ESPN, "Grand-Am and ALMS merge into United SportsCar Racing," accessed 11 June 2026, https://www.espn.co.uk/racing/alms/story/_/id/9053893/grand-alms-merge-united-sportscar-racing. ↩ ↩²

5. FIA WEC, "Major global marques headline 2026 FIA WEC entry list," accessed 11 June 2026, https://www.fiawec.com/en/news/major-global-marques-headline-2026-fia-wec-entry-list/8580. ↩

6. IMSA, "IMSA GTP Field Nearly Complete for 2026 Entering December," accessed 11 June 2026, https://www.imsa.com/news/2025/12/03/imsa-gtp-field-nearly-complete-for-2026-entering-december/. ↩ ↩²

7. IMSA, "Cadillac Wins Motul Petit Le Mans as Champions Crowned," accessed 11 June 2026, https://www.imsa.com/news/2025/10/11/cadillac-wins-motul-petit-le-mans-as-champions-crowned/; RACER, "Whelen Cadillac wins Petit Le Mans as Porsche crowned IMSA GTP champions," accessed 11 June 2026, https://racer.com/2025/10/11/Whelen-Cadillac-wins-Petit-Le-Mans-as-Porsche-crowned-IMSA-GTP-champions. ↩

8. NASCAR, "Porsche Penske Motorsport collects third straight Rolex 24 win at Daytona," accessed 11 June 2026, https://www.nascar.com/news-media/2026/01/25/rolex-24-at-daytona-recap-porsche-penske-third-straight-win/; NBC Sports, "2026 Rolex 24 results: A Porsche Penske three-peat as Felipe Nasr closes another win," accessed 11 June 2026, https://www.nbcsports.com/motor-sports/news/2026-rolex-24-results-porsche-roger-penske-motorsport-three-peat-felipe-nasr-win-imsa-daytona-international-speedway. ↩

9. IMSA, "Full Fields Continue For 2026 IMSA WeatherTech Championship, Michelin Endurance Cup," accessed 11 June 2026, https://www.imsa.com/news/2025/10/09/full-fields-continue-for-2026-imsa-weathertech-championship-michelin-endurance-cup/. ↩