The 24 Hours of Le Mans
This race is synonymous with the sport. While at times a part of various series, it has always been organized independently by the ACO. Often cars appear only here and at no other races, so it deserves to be its own category.
Period From To
The Ford GT40 era 1966 1969
The Porsche 917 era  1970 1971
The 3-litre era   1972 1977
The Porsche 936 era   1978 1981
The Birth of the Group C era   1982 1985
The golden age of Group C 1986 1990
The long, slow, agonizing death of the Group C era 1991 1994
The Mclaren F1 and the 'GT1' revolution 1995 1996
Prototype & GT1 Smackdown 1997  
Factory Battle Royal 1998
Mercedes re-enacts 1955 (sort of) 1999
Audi smokes 'em all 2000
Audi smokes 'em all again 2001
Audi smokes 'em all again 2002
Bentley rolls on. 2003
The Privateer Audi Era 2004 2005
The R10 Diesel Era 2006 2008
The Audi/Peugeot Diesel Era 2009 2011