(CNN) — -- A light rain was expected Saturday evening for the 139th Kentucky Derby, where two riders were making a run for history.
By 4 p.m., more than a third of an inch of rain had fallen at Louisville's Churchill Downs, where the main track was labeled as sloppy. The race is scheduled for 6:24 p.m. ET.
Among the favorites in the 19-horse field are Revolutionary, Orb, Verrazano and Goldencents.
Goldencents will be ridden by Kevin Krigger, vying to become the first black jockey to win the premier race since Jimmy Winkfield took the trophy back-to-back in 1901 and 1902.
"If someone is going to be the first African-American in 111 years to do it, then why not me?" the 29-year-old from the Virgin Islands said before the race.
Rosie Napravnik, 25, is making a bid to be the first female jockey to win the Kentucky Derby.
"I'm very physically fit. I'm strong. I'm not just a little string bean female that weighs 100 pounds -- and that's why I ride horses," she told CNN.
Napravnik, riding Mylute, is the fifth-highest-earning jockey on the circuit today. Last year the horses she rode finished in the top three in nearly half the races she entered and won more than $12.4 million.
Nicknamed the Run for the Roses, for the garland that is draped over the winner, the Derby traces its rich history back to 1875, when Col. Meriwether Lewis Clark Jr. decided to inaugurate a race in his home state of Kentucky.
The Derby is the first jewel of the Triple Crown. The 138th running of the Preakness, on May 18 in Maryland, is the second, followed by the Belmont Stakes, in New York on June 8. Only 11 horses have won the crown, and none has since Affirmed in 1978.
More than an inch of rain fell before the 2012 race, giving weather to partly sunny skies by race time.
Tom Reaugh, a meteorologist at the National Weather Service Office in Louisville, recalled sloppy conditions in the 2010 race. But the sun came out at the gate.
Being in the city for the two-week derby celebration is a treat, regardless of the weather, Reaugh told CNN.
"The ladies still wear the hats, the men have on their suits and everyone has a good time."
CNN's Sheena McKenzie and Francesca Cumani contributed to this report.