Are Kentucky Derby Horses All Male

 Are All The Kentucky Derby Horses Male? Even though male

 horses are not able to take part at the Kentucky Derby race, 

it's an anomaly in the race. To give you an idea, colts and horses

 typically weigh around 126 pounds while fillies are typically

 carrying the weight of 121 pounds. Both races are conducted in

 different lengths.

Have female horses been crowned winner of the Kentucky Derby?

 Only three fillies have taken home in the Derby: Regret (1915), 

Genuine Risk (1980) and Winning Colors (1988) However, 

the idea that they're overmatched to the best colts is not 

supported by the numbers. Out of the forty fillies who have 

competed in the Derby 10 have been within the top three.

There's no sex requirement when racing horses at the Kentucky

 Derby, only an age restriction: the horses must be registered as

 three-year-olds. However, in practice fillies do not usually 

compete in these Triple Crown races. A majority of U.S. trainers

 prefer to have their fillies compete in (more than or less) 

similar distaff races, like those at the Kentucky Oaks.

In the past the eligibility criteria for The Kentucky Derby 

was determined by the earnings of stakes races that were

 graded. Females had the same chances to earn money as 

males did. In 2013, to be eligible for the Derby participants 

had earn points at certain qualifying races. The races begin

 the year prior to the top two-year-old races. Races that qualify 

for Derby are different from Kentucky Oaks. Kentucky Oaks. 

Thus, a trainer with an outstanding filly needs to choose early

 the race they want to target.

But, there have been fillies who have been in the Derby and 

three have been winners. The first horse to win in the race 

was Regret from 1915. The second one was Genuine Risk in

 1980, and the last one to win was Winning Colors in 1988.

 Winning Colors took home the Santa Anita Derby and would

 probably have qualified according to the points system.