The Triple Crown of Thoroughbred Racing consists of the Kentucky Derby, the Preakness and the Belmont. As of 2009, there has been no Triple Crown winner for thirty-one years.
The last horse to win the Triple Crown was Affirmed, in 1978.
There were two other Triple Crown winners in the nineteen-seventies: Seattle Slew, in 1977, and Secretariat, in 1973.
Before that, you have to go all the way back to 1948 to find a Triple Crown winner: Citation.