Her first space mission lasted 147 hours, but the implications of it stretched much farther into the future. Her flight opened the door for dozens of other American women ? 30 to date ? to fly into orbit.

Since then, women in the space program have soared. Astronaut Shannon Lucid holds the record for time spent in space -- more than any other woman in the world. In 1999, Eileen Collins became the first female Shuttle commander. She is also poised to command the first Shuttle mission when the fleet returns to flight following the Columbia accident.

Ride's unprecedented journey began in 1977, when she saw a help-wanted ad in the newspaper. It said NASA was looking for scientists -- not just pilots -- for its astronaut corps. The new, reusable spacecraft the agency was planning to deploy, the Space Shuttle, would need the scientists as "mission specialists" to carry out research and other tasks.

Ride was one of five women selected to the astronaut class of 1978. She was the only woman in a crew of five when the Space Shuttle Challenger took her on her first mission. Ride was an instant celebrity; schoolchildren everywhere knew her name. In an instant, little girls learned that even the sky wasn't the limit.

"I think Sally was more representative of a profound cultural change where the world was ready to have a woman in that kind of job," said Astronaut Pam Melroy, who graduated from college around the time of Ride's first flight.

Twenty years after her historic mission, Ride is involved with human space flight again. She is using her expertise as a member of the investigative panel looking into the Space Shuttle Columbia accident, a role she also played during the Challenger investigation.