With support from NASCAR's Bill France, John Bishop formed the International Motor Sports Association (IMSA) in 1969 and its first race attracted a crowd of precisely 348 spectators! Over the next two decades, the series grew into a professional sports car championship with the Daytona and Sebring endurance classics at its heart.
A six-race inaugural GT Championship for road-based sports cars was organised in 1971. The calendar was expanded a year later with long-time backers Camel cigarettes as title sponsors for the first time. GT was subsequently replaced by GT Prototypes (GTP) and then World Sports Cars (WSC) as IMSA's headline category.
IMSA (or Camel) Lights was a successful secondary class for prototypes that ran from 1985-93. The GTO, GTU and then GTS divisions added competitive depth to the field and maintained IMSA's links to production sedans.
Peter Gregg and Al Holbert were perennial champions during the 1970s and 1980s although both met untimely deaths. The series was also engulfed in drug scandals during the mid 1980s with Randy Lanier and members of the Whittington and Paul families implicated.
Geoff Brabham's Nissan and then Juan Manuel Fangio II's Eagle-Toyota dominated at the start of the 1990s during a time of change for the organisation. Having undergone heart surgery in 1987, Bishop sold his interests two years later with businessman and sometime racer Andy Evans eventually assuming control.
New World Sports Car (WSC) rules were introduced 1994 and North America's premier endurance series was run to those rules for the next five years. Races were sanctioned by Evans' new Professional Sports Car Racing (PSCR) organisation from 1997-98 before the series was superseded by the American Le Mans Series.