BALTIMORE — Girls rule!

The best 3-year-old in the land just happens to be a filly named Rachel Alexandra.

Jockey Calvin Borel all but guaranteed victory in the Preakness Stakes and, boy, did she deliver, becoming the first filly in 85 years to win the second leg of the Triple Crown.

A rangy bay — as big as most of the horses she beat — Rachel Alexandra shot to the front yesterday and wasn't seriously challenged until a late close by Kentucky Derby winner Mine That Bird.

By beating him she ended any chance that thoroughbred racing would have a Triple Crown winner this season. Affirmed was the last Triple Crown winner in 1978.

Rachel Alexandra led by a head at the quarter and half-mile poles. She stretched it to a half-length at the three-quarters pole. She was ahead by four lengths going down the stretch. In the end, the 9-5 favorite won by a length in her first race against the boys.

The win also validated Borel's decision to climb off Mine That Bird and stay on the filly as her regular rider.

Now Borel may get a shot at a personal Triple Crown, if Rachel Alexandra goes on to the Belmont Stakes in three weeks. The 1 1/2-mile race is the most grueling of the three.

"I'm not worried about nothing," he said. "It's going to take a racehorse to beat her."

Rachel Alexandra had already beaten up on her own gender, winning her five previous races by a combined 43 1/2 lengths.

Musket Man finished third, as he did in the Derby, followed by Flying Private and Big Drama.

Rachel Alexandra covered 1 3-16 miles in 1:55.08 and became the first horse to win at Pimlico from the No. 13 post on the far outside. She paid $5.60, $4.60 and $3.60. Mine That Bird returned $6.60 and $4.80, while Musket Man paid $5 to show.

"I'm thrilled to death with the race my little horse ran," said Chip Woolley Jr., who trains Mine That Bird. "You have to give that filly credit. She's a great one."

Rachel Alexandra earned $660,000 from the purse of $1.1 million.

Papa Clem was sixth, followed by Terrain, Luv Gov, General Quarters, Friesan Fire, Pioneerof the Nile, Tone It Down and Take the Points.

The last filly to win the Preakness was Nellie Morse in 1924. Rachel Alexandra became the second filly to go off as the wagering favorite and win. Whimsical at 8-5 odds was the first, in 1906.

Rachel Alexandra stumbled slightly leaving the gate, then stuck her head in front at the first turn and refused to give way.

Her first challenge was to get rid of Big Drama, a persistent presence from inside down the backside and into the final turn. Once she shook him loose and opened up the four-length lead at the top of the stretch, Mine That Bird made a run at her.

Borel sensed she was tiring, and took firm hold of the reins.

"I had to put the bit in her mouth because she was kind of struggling," he said. "It kind of took a lot out of her."

Still, she had enough left at the end and crossed the finish line to the cheers of 77,850 fans — the smallest crowd since 1983 — at Pimlico.

"Awesome," said Bob Baffert, who trains Pioneerof the Nile. "Rachel Alexandra is amazing. She took the heat and kept on going."

The most impressive of Rachel Alexandra's performances was her stunning victory by 20 1/4 lengths in the Kentucky Oaks, the day before the Kentucky Derby.

This ending was far different from the last time a filly challenged the boys. Eight Belles finished a gallant second in last year's Kentucky Derby, then broke both front legs while galloping past the finish line and was destroyed on the track.

This time, it was all cheers. No tears.

"Rachel Alexandra was great," trainer Todd Pletcher said. "She took it right to them, led every step of the way. She deserves a lot of credit."

Rachel Alexandra, marked by two white spots on her head, wasn't even supposed to be in the Preakness. Her original owners, who named the filly after a 13-year-old granddaughter, didn't nominate her to the Triple Crown races, believing fillies should run only against their own gender.

After the Oaks, Rachel Alexandra was sold to Jess Jackson, founder of Kendall-Jackson winery, and Harold McCormick.

They ponied up $100,000 to buy her a spot in the race, and the gamble paid off.

"There was a lot of social criticism and doubt about whether she was capable," Jackson said. "I think I would've taken some heat if she hadn't performed well, so that takes some heat off my shoulders."

Borel had total faith in the filly, making the unprecedented decision to dump Mine That Bird after his stunning Derby victory at 50-1 odds.

"She's the best horse in the country right now, bar none," he said.

The start of the Preakness was delayed slightly when Big Drama reared up in the gate and dumped his rider. Rachel Alexandra stood at the opposite end, waiting patiently for the biggest test of her life.

Unlike the Derby, Mine That Bird had a tougher trip with Mike Smith, Borel's replacement, aboard. A light rain fell at the start of the race, but it didn't turn the dirt track into the kind of slop that he flew through to win at Churchill Downs.

"My hats off to her. She's a talented, talented mare," Smith said. "Anyone else would have caved."