The 50th International 500-Mile Sweepstakes was held at the Indianapolis Motor Speedway in Speedway, Indiana on Monday, May 30, 1966. The official program cover for the race celebrated both the 50th running of the race, and sesquicentennial (150th anniversary) of Indiana statehood.

Eleven of the 33 starters were eliminated in a first-lap accident right after receiving the green flag on the main stretch. Only A. J. Foyt was injured, hurting his hand scaling the catch fence trying to escape the wreck scene. Only seven cars, the fewest finishers ever, were still running by the end of the race.

First-time starter Jackie Stewart led by over a lap late in the race in John Mecom's Lola T90-Ford. However, inside ten laps to go, his oil pressure dropped too low due to a broken scavenge pump. Stewart parked the car, and walked back to the pits. Fellow rookie Graham Hill inherited the lead and led a total of 10 laps to win, the first rookie winner since 1927. Despite parking the car, Stewart was voted the rookie of the year over Hill.

Defending race winner Jim Clark spun twice during the race, and finished second. For the second year in a row, the Wood Brothers from the NASCAR Grand National circuit were invited to work pit stops, this time for Dan Gurney. However, the car dropped out of the race in the crash on the opening lap.

* Includes days where track
activity was significantly
limited due to rain

Three-year veteran Johnny Rutherford was injured in a serious crash on April 3 at Eldora, and was forced to sit out the 1966 race.

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