WASHINGTON — More than half a century after Rosa Parks helped kindle the civil rights movement by refusing to give up her seat on a segregated bus in Alabama, she has become the first black woman to be honored with a life-size statue in the Capitol.

At a dedication ceremony on Wednesday that was attended by dozens of Mrs. Parks’s relatives, President Obama and Congressional leaders paid tribute to Mrs. Parks, whose act of defiance and work in the civil rights movement helped spur desegregation across the country and the passage of the Voting Rights Act. Almost simultaneously with the ceremony, the landmark law was facing a legal challenge at the Supreme Court, across the street from the Capitol.

“This morning, we celebrate a seamstress, slight of stature but mighty in courage,” Mr. Obama said.

The statue of Mrs. Parks captures her waiting to be arrested on Dec. 1, 1955, after she refused to give up her seat for a white passenger on a crowded segregated bus in Montgomery, Ala. She is seated, dressed in a heavy wool coat and clutching her purse as she looks out of an unseen window waiting for the police.

“In a single moment, with the simplest of gestures, she helped change America and change the world,” Mr. Obama said.