Just over two minutes later, a winner will emerge and thoroughbred racing will have its newest contender for a Triple Crown. The Preakness follows in two weeks and the Belmont Stakes is June 8. The last horse to sweep all three races was Affirmed in 1978.
Black Onyx was scratched from the race on Friday.
NBC televises the 1¼-mile race from 4 p.m.-7 p.m. The purse is $2,199,800, with $1,439,800 to the winner.
Here's a running account of the event and everything going on around it, with journalists from The Associated Press bringing the flavor and details of everything surrounding the race.
HUMANA DISTAFF: Aubby K, the 7-2 favorite, rallied past Burban to win the $345,600 Humana Distaff for fillies and mares. Edgar Prado guided the 4-year-old through the slop to get up by 1 ½ lengths for her second straight stakes victory.
MORE SLIDING, FEWER CUFFS: The normally rowdy infield crowd at the Kentucky Derby appears well behaved.
As the rain comes down, fans have taken to sliding across water-slickened tarps and muddy stretches in a makeshift slip-and-slide.
Louisville Police Officer Carey Klain said as of mid-afternoon, only two people had been arrested and three cited for ticket scalping.
"So far, so good," Klain said.
While the area under the grandstand is crowded, people are milling about and moving through slowly but efficiently.
IT'S SO RAINY...: How rainy is it at Churchill Downs?
Even the bugler is wearing a red poncho as he blows the call to the post in the early races.
STAT CHECK: This stat check comes from ESPN sports business reporter Darren Rovell. According to Rovell, roughly 5.1 million ounces of beer will be consumed at the Kentucky Derby.
That's nearly 319,000 16-ounce pours.
UNDERCARD RACE: Berlino Di Tiger held off Chamblerlain Bridge by a nose to win the $138,250 Twin Spires Turf Sprint, the first stakes on the Derby Day program at Churchill Downs.
Making his third start in the U.S. after beginning his career in Brazil, Berlino Di Tiger pulled the 11-1 upset with Leandro Goncalves aboard.
Chamberlain Bridge showed he is still going strong at 9. He won the Breeders' Cup Turf Sprint here in 2010.
THE LONGSHOT: With $11,2 million wagered and a little more than four hours before post time, Falling Sky is getting the least love from bettors. The horse trained by John Terranova II and ridden by Luis Saez was at 37-1 odds.
GAMBLERS ABOUND: Among the actors, musicians and athletes arriving on the red carpet are a fitting type of celebrity for a horse race: Poker players.
Imagine that, gamblers at the Kentucky Derby.
Among them is Phil Hellmuth, who's won 13 gold bracelets and $12.2 million at the World Series of Poker and is known to place a bet or two beyond the felt. He tweeted a picture (http://bit.ly/10duKeu ) of himself, with "The Voice" contender Nicholas David and actress Jennifer Tilly — all posing with the Stanley Cup. Makes sense, we guess.
Fellow poker player Robert Williamson dressed in all black and white, from his hat to his shoes, with one exception — socks covered in sometimes neon-colored daisies.
"They give me a little color," Williamson said.
Tilly, a poker player herself, glided onto the red carpet to cheers from a large throng of onlookers assembled under a canopy near food and booze vendors at Churchill Downs. Tilley, who voices some characters on "Family Guy," agreeably posed as photographers shouted requests: "Look this way please!" ''Can you pose to the right?"
TRACK CONDITIONS: David Lehr, the Churchill Downs track superintendent, has downgraded the main track to "sloppy" due to consistent rain falling Saturday morning and early afternoon. The track is now "sealed," or packed down so that excess water rolls off rather being absorbed in the surface.
Track conditions could continue to change before the Kentucky Derby, the day's 11th race.
Only eight of the 19 Derby runners have ever run on a dirt track rated worse than "fast."
Normandy Invasion is one of the 11 never to have run on an off track but trainer Chad Brown hoped this morning that his colt would take to the possibility of a sloppy surface.
"I'm told his breeding is good for the mud," Brown said. "I see that go both ways. Sometimes it does prove to be true and sometimes even if they're bred for it, they don't run in it. You really don't know until you try it."
$1M MARK: Revolutionary is the first Kentucky Derby horse with $1 million in bets. The 5-1 favorite passed the mark with $8.3 million in total wagers at Churchill Downs.
CELEBS ARRIVING: The famous faces are starting to arrive. Among the sightings: National anthem singer Martina McBride, TV personality Star Jones, basketball greats Julius "Dr. J" Erving and Scottie Pippen, Speaker of the House John Boehner, New England Patriots lineman Vince Wilfork, actor Anthony Anderson and actress Valerie Harper, who was recently diagnosed with terminal brain cancer.
QUICKQUOTE: TIGHT SECURITY: "The more, the merrier, as far as I'm concerned." — Frank Hanlon, 31, of Memphis, Tenn., on added security joining at Churchill Downs in response to the bombings at the Boston Marathon last month. Kentucky National Guardsmen searched bags and passed metal detecting wands over race goers, while raincoats, towels and small cameras were being inspected.
SLOPPY DERBY: The last Kentucky Derby run on a track listed as sloppy was in 2010, when Calvin Borel rode 8-1 Super Saver to victory. That day, 1.32 inches of rain fell at Churchill Downs. Saturday's forecast calls for the rain to become progressively steadier as post time approaches.
Borel also won on a sloppy track in 2009 when 50-1 shot Mine That Bird splashed home first. The jockey nicknamed "Bo-rail" because of his rail-hugging rides at Churchill will be aboard Revolutionary in the Derby.
I'VE GOT A SYSTEM: Betting strategies at the Kentucky Derby vary as wildly as the hats.
Some racing fans plan out their wagers days in advance, poring over statistics and previous races to make an informed decision. But many fly by the seat of their pants, choosing an interesting looking horse or colorful jockey silks.
"I love cats," said Shelly Dozier-McKee of Atlanta, who decided to bet on Charming Kitten in the Derby. It's her first trip to Churchill Downs, and Dozier-McKee said she received some betting tips from former University of Louisville coach Denny Crum during a party Friday night.
She said Crum, who won two NCAA basketball championships, showed her how to bet exactas and trifectas, she said.
"I got some good insider tips from him," Dozier-McKee said from under a black, wide-brimmed hat adorned with a feather.
Jeremy Hewson learned how to bet horses from his grandfather back in Greenfield, Ind. He'll study the racing form, looking at speeds and performances in past races.
Hewson said the rainy track would factor into his picks, but so far he likes Verrazano in the Derby.
"Unless I see something that changes my mind," he said.
BACK TO THE SCENE: Steve Cauthen recalls the night before he won the 1978 Kentucky Derby with Affirmed, he slept on the floor of a motel room that housed five people.
"I slept like a baby," he said. "I knew no one would bother me down there."
Cauthen, then 18, got up the next day and won the race, setting him and Affirmed on an odyssey that culminated in winning the Triple Crown. No one horse has swept the Derby, Preakness and Belmont since then.
"It was a great time in my life," said Cauthen, who turned 53 this week. "I was living my dream."
He was at Churchill Downs on Saturday serving as a celebrity handicapper for Derby Experiences, a custom travel program for racing fans. Cauthen's Derby pick? Revolutionary, if the dirt surface turned sloppy as expected.
WHERE'S WALDO?: Where's Waldo? On the infield at Churchill Downs.
Andy Deron, 25, of Chicago, aka "Where's Waldo?," partied early on a soggy infield Saturday while scouting out horses for the Kentucky Derby later in the day. Deron's costume, based on the children's book series, stood out amid a variety of rain coats, homemade hats and colorful dresses and suits during an overcast, rainy day at the track.
Deron and several friends meet each year on the infield to enjoy the party.
"You never know what's going to happen on the infield," Deron said.
Other infielders are wearing rubber boots or even high heels as the rain turns grass and dirt into mud. April Pauley of Columbus, Ohio, paraded around in the mud wearing a hat featuring flowers, a papier-mache jockey head and goggles and ribbons.
"It's just my own little creation," Pauley said before taking a swig of a beer.
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ODDS WATCH: Orb, who? The morning favorite is no longer the horse bettors at Churchill Downs like most.
Just after noon, with $6.8 million wagered, Revolutionary has shot up to become the race's favorite at 5-1, with nearly $831,000 in bets, according to live odds on the Kentucky Derby's website.
Goldencents is 6-1 while Orb and Normandy Invasion are at 7-1.
THE ESSENTIALS: The liquor is flowing as much as the rain on the infield at Churchill Downs.
Michael Frankenberger and Eryn Murphy, both from Sellersburg, Ind., are working the Cox's Smokers Outlet tent. Race goers didn't seem to mind lighting up in the rain, although the husband and wife expect sales to increase as the day goes on.
As people wander the infield, booze and bites are prevalent, with mint juleps and grilled turkey legs appearing to be among the most popular items.
Murphy said cigars and booze were part of the Kentucky Derby experience.
"I think it's a matter of a cigar in one hand and a mint julep in the other to get a feel for the Derby," Murphy said.
WHIMSICAL WAGERS: For the casual racing fan interested in making a bet on the Kentucky Derby, here's a few whimsical wagers you might want to consider. Of course, any astute handicapper will laugh this off, but it's the Derby and anything goes when a large field of 3-year-olds run farther (1¼ -miles) than they have before or will again. Can you say 50-1 long shots Giacomo and Mine That Bird?
With that in mind, here's a trifecta of exotic bets to consider:
— The O-my! $1 trifecta box — Oxbow, Orb, Overanalyze. A $1 trifecta box on these horses, numbers 2-9-16, will cost $6. If the three come in first, second and third — in any order — you'll cash a fairly lucrative ticket.
— The golden $2 exacta box: A $4 bet on Golden Soul and Goldencents, numbers 4-8, pays off if the horses are the top two finishers.
— The War Horse $1 four-horse Superfecta box: Revolutionary, Normandy Invasion, Lines of Battle and Java's War, or the 3-5-11-19 combination. A $1 box sets you back $24, but the payoff will be in the many thousands of dollars if those horses are the top four finishers — in any order.
PLASTIC IN: The Kentucky Derby is known as much for hats and high fashion as it is for fast horses. But today, plastic wrap and boots are accenting many of the vibrant colors, dresses and suits.
The rain started early, drizzling lightly with heavier downpours expected later. That hasn't stopped people from wearing leopard-print suits, short dresses and feather-laden hats with high heels.
Many took the precaution of wearing ponchos or plastic bags over the fancy duds in a sometimes losing effort to protect their sartorial investments. But for those who didn't, well, rain's just a part of the experience.
QUICKQUOTE: ON THE RAIL: "For the real troopers, Derby fans, you gotta stick it out. It ain't nothing but another day. I've got to work in the rain so it don't hurt my feelings none." — Derby fan Lanny Westfall of Louisville, who arrived at 6 a.m. to claim a patch of grass to watch the race along the backside rail. His group's setup had about 20 camping chairs and a four-burner gas grill ready for burgers, bratwurst and pork loin.
ANTHEM BREAK: Lines at the betting windows at Churchill Downs are filling up as people look to place wagers on the Run to the Roses as well as a slew of earlier races.
The paddock area near the betting windows was a flurry of photos and chatter until the national anthem played over the public address system. Then, people turned toward an American flag flying over the historic racetrack as things grew silent and people stopped sipping beer, champagne and bourbon. A few race goers in bow ties, fancy hats and seersucker suites saluted.
A round of applause broke out at the end of the anthem and a discussion of horses, drinks and dresses resumed.
PLETCHER LIGHT, BUT FOCUSED: The mood around Todd Pletcher's Barn 34 has been light but focused as the trainer prepares to run a record-tying five horses.
After watching his colts stretch their legs in the shedrow this morning, Pletcher sat in his barn office at 7:15 a.m. with father, J.J., and son, Payton.
"All the Derby horses just walked and everybody seems to be in good order," he said.
A win from one of his five — Revolutionary (No. 3), Overanalyze (No. 9), Palace Malice (No. 10), Verrazano (No. 14) and Charming Kitten (No. 15) — would give the 45-year-old conditioner the first sweep of the Derby and the Kentucky Oaks since 1952.
Princess of Sylmar, one of four Pletcher fillies in the race, took the Oaks by a half-length on Friday, paying a whopping $79.60.
The celebration was low key at the hotel.
"We all met in kind of a conference room there and had some pizza, just friends and family," Pletcher said. "Same thing we do every year, win, lose or draw."
Back at the track early as always, Pletcher started his busy Derby day with a ham and Swiss sandwich, topped with a packet of mustard, for breakfast.
"It's what they delivered so it's what I'm going to eat," he said.
THE SETUP: Orb, the Florida Derby winner, is the 7-2 morning-line favorite, with unbeaten Verrazano next at 4-1. Santa Anita Derby winner Goldencents is the third choice at 5-1, and is trained by Doug O'Neill, who won the Derby last year with I'll Have Another.
Trainer Todd Pletcher has a record-tying five horses in the race — Verrazano, Revolutionary, Overanalyze, Palace Malice and Charming Kitten.
D. Wayne Lukas, at 77, could become the oldest trainer to win the race. The four-time Derby winner has two chances in long shots Oxbow and Will Take Charge.
There could be some jockey history, too: Kevin Krigger, who rides Goldencents, would be the first black jockey to win the Derby since 1902; and Rosie Napravnik, aboard Mylute, would be the first female to win.
The forecast around race time calls for temperatures in the low-60s and calls for temperatures in the mid-60s and a 80 percent chance of rain. A crowd of about 160,000 is expected.
The purse is $2,199,800, with $1,439,800 to the winner.
UNDER NO UMBRELLAS: AP's Louisville correspondent Janet Cappiello says it began raining at Churchill Downs before she arrived at the track, so people are trickling in when normally they'd be streaming in. The track doesn't allow umbrellas so people are using the next best thing — ponchos.