According To Wikipedia and the Preakness Website:
"Historic Pimlico Race Course, home of the Preakness Stakes and second oldest racetrack in the nation behind Saratoga, opened its doors on October 25, 1870. Pimlico has hosted many racing icons for over a century; legendary horses such as Man o’ War, Sir Barton, Seabiscuit, War Admiral, Citation, Secretariat and Cigar have thundered down her stretch in thrilling and memorable competition."
"In the United States, the Triple Crown of Thoroughbred Racing, commonly known as the Triple Crown, is a title awarded to a three-year-old Thoroughbred horse who wins the Kentucky Derby, Preakness Stakes, and Belmont Stakes. The three races were inaugurated in different years, the last being the Kentucky Derby in 1875. These races are now run annually in May and early June of each year. The Triple Crown Trophy, commissioned in 1950 but awarded to all previous winners as well as those after 1950, is awarded to a Triple Crown winner."