Glossary Updated April 21, 2025 By Lines.comPreakness StakesThe second of three Triple Crown of Thoroughbred horse races. The event is held annually at the Pimlico Race Course in Baltimore, Maryland. The Grade I race is approximately 1 3/16 miles and the competitors are three year old Thoroughbreds. The race is held in the middle of May and is considered one of the popular betting events in horse racing.