Video: Listen to Explanation of Maximum Security's 2019 Kentucky Derby DQ

For the first time in the 145-year history of the Kentucky Derby, the unofficial first-place finisher was disqualified.

Maximum Security, which entered the race with 9-2 odds, led for the majority of the race and wound up crossing the finish line first for an apparent victory:

However, Flavien Prat, the jockey of second-place finisher Country House, objected to a move made by Luis Saez and Maximum Security. 

That objection led to a lengthy review, where it was ultimately determined that Maximum Security impeded the path of War of Will and got in the way of Long Range Toddy:

With that, Maximum Security was disqualified, leading to Country House taking home the roses. According to ESPN Stats & Info, Country House (65-1) becomes the second-biggest underdog to win the Kentucky Derby. Donerail overcame 91.5-1 odds in 1913.