The mint julep became the Kentucky Derby’s signature drink in 1938 and unintentionally created what would eventually become the race’s leading collectible: the Kentucky Derby glass. That first year, the juleps were served in water glasses. According to racetrack folklore, the glasses were so popular that they disappeared from the tables in the track’s dining rooms. The next year, track management charged dining room patrons an extra 25 cents to keep the glass.
Today, the value of a Kentucky Derby glass as a collectible is based on its rarity. From 1938 through 1952, fewer than 100,000 glasses were produced each year. In 1966, that number rose to 250,000; it was upped to 400,000 for the 100th running of the race in 1974. That was also the first year that the glasses could be purchased outside Churchill Downs. The current production number is 700,000 glasses per year.
Source: The Kentucky Derby Museum