Jockey Bobby Ussery flashes the victory sign on May 4, 1968, atop Dancer’s Image in the winner’s circle of the 94th Kentucky Derby at Churchill Downs in Louisville. Dancer’s Image was later disqualified and was placed last because of a positive drug test after the race. He is the only Derby winner to have been disqualified in the 143-year history of the race. Traces of phenylbutazone, known as bute, were found in Dancer’s Image’s post-race urinalysis. It was legal at some tracks at the time, but Churchill Downs wasn’t one of them. Today, the anti-inflammatory is one of the most commonly used drugs in horse racing, given to alleviate chronic pain and joint inflammation and not to enhance performance. Kentucky medication rules allow any of the 20 horses running in Saturday’s Derby to be given bute more than 24 hours before the race, provided their post-race sample doesn’t exceed a specified amount. Calumet’s Forward Pass became the winner of the 94th Kentucky Derby. Herald-Leader Archive Photo