OMAHA - Rachel Bootsma didn't want to say how fast she might swim Wednesday night. She had a time in mind, but she chose to keep it to herself.

But Tuesday night, she might have been setting the bar a little higher, after the number that popped up on the scoreboard in the semifinals of the women's 100-meter backstroke at the U.S. Olympic trials.

Bootsma, of Eden Prairie, slashed through the CenturyLink Center pool in 59.10 seconds to win her heat. Moments later, her friend Missy Franklin upped the ante, winning her heat in 59.06 to set up a showdown of young stars in Wednesday's finals.

A crowd of 12,131 roared for Bootsma, 18, who dropped .55 of a second off her previous personal best. Franklin, 17, also swam the fastest time of her career. Their times were the second- and fourth-fastest in the world this year and impressed even Natalie Coughlin, who has won the past two Olympic gold medals in the event.

Coughlin also made the final, going 1:00.63 for the seventh of eight spots. But Bootsma and Franklin stole the show, cranking it up a notch after starting the day with stellar swims in the preliminaries.

"I am surprised," said a giddy Bootsma, who smiled broadly when she checked the scoreboard after her swim. "I still have a couple of things to work on for [the finals], but overall, I'm really pleased. Missy is a great competitor and a great friend of mine. It will be fun to be in the finals with her."

Bootsma swam what then was the second-fastest time of her career -- 59.69 seconds -- in the morning preliminaries. Only Franklin swam faster, recording a 59.54.

Another Minnesotan, David Plummer of Minnetonka, also made Wednesday's finals in the men's 100 backstroke by swimming the second-fastest qualifying time in Tuesday's semifinals (53.24).

The Olympic roster continued to fill up after three more finals Tuesday night. Dana Vollmer, who set an American record of 56.42 Monday night in the semifinals of the 100 butterfly, won the finals in 56.50 seconds, with Claire Donahue second. Allison Schmitt and Chloe Sutton went 1-2 in the women's 400 freestyle, and former retiree Brendan Hansen kept his comeback going with a victory over Eric Shanteau in the men's 100 breaststroke.

To prevent herself from being overwhelmed this week, Bootsma has told herself that the trials are the same as any meet. And to underscore that, she is following the same routine: the afternoon naps, the chocolate, the reality TV shows before bedtime. She came to watch the first night of the trials Monday, but coach Kate Lundsten sent her back to the hotel at 8 p.m. so she could rest.

Bootsma's mother, Jan, asked her if it made her more nervous to see the opening-night hoopla, which featured indoor fireworks, flames shooting from the pool's edge and more American flags than a July 4th parade. It did, Rachel said, but she could handle it. "Everybody else is nervous, too," she said. "We're all going through the same thing."

Monday's preliminaries in her first event, the 100-meter butterfly, got rid of the initial jitters, as Bootsma swam a personal-best time of 1:00.13 to finish 23rd. Tuesday, she was just as happy about her opening swim in the 100 back. Though Lundsten thought she looked a little tight in her opening 50 meters, Bootsma was pleased to record a swift time while knowing she could make some minor adjustments to get faster.

She did so Tuesday night, easily winning her heat. Parents Jan and Rob Bootsma rejoiced in the stands, along with friends and relatives who made the trip to Omaha. Bootsma's growing legion of fans cheered, too. Even other swimmers had high praise for Bootsma and Franklin.

"I'm happy for them," Coughlin said. "Rachel is swimming awesome. Missy is swimming awesome. Elizabeth [Pelton] is swimming awesome."

Bootsma originally planned to swim the preliminaries of the 200 individual medley Wednesday morning. Instead, she will get a little extra rest for the race of a lifetime, with a spot on the Olympic team in her sights.

"I'm so excited, but I'm extremely nervous," Bootsma said. "This is what you work for."