The 1968 United States Road Racing Championship season was the sixth and final season of the Sports Car Club of America's United States Road Racing Championship. It began March 31, 1968 and ended August 18, 1968 after nine races. Mark Donohue won the season championship. The series would be revived thirty years later, but only for two years before becoming the Rolex Sports Car Series. Taken from http://en.wikipedia.org/wiki/1968_United_States_Road_Racing_Championship_season.

The 1968 24 Hours of Le Mans was the 36th Grand Prix of Endurance, and took place on 28 and 29 September 1968. It was the tenth and final round of the World Sportscar Championship.
The race was originally planned for June 15 and 16, but had to be delayed until September due to massive protests in France during May. The rescheduled race increased the chances of the Prototypes against the Sports, as the new Prototype cars had matured during the season. Taken from http://en.wikipedia.org/wiki/1968_24_Hours_of_Le_Mans