Photos: See scenes from the Kentucky Derby

The Kentucky Derby, the oldest continuously held major sporting event in the United States, celebrates its 150th anniversary Saturday with a new $200 million paddock and a host of safety initiatives aimed at curbing the horse deaths that marred last year's event.

Churchill Downs' partygoers will wear colorful hats and sip $22 mint juleps from souvenir glasses beneath the twin spiers that stand like sentinels above this cathedral of horse racing. From the first Derby, won by Aristides in 1875, to this year's race, one constant has remained.

When the announcer says, “And they're gone,” everyone involved in bringing in the country's best three-year-old Thoroughbreds, from the owners to the trainers to the grooms, holds their breath and hopes their horse gets through first the finish.