But there was another woman, named Claudette Colvin, who refused to be treated like a substandard citizen on one of those Montgomery buses — and she did it nine months before Mrs. Parks. The Rev. Dr. Martin Luther King Jr. made his political debut fighting her arrest. Moreover, she was the star witness in the legal case that eventually forced bus desegregation.

Yet instead of being celebrated, Ms. Colvin has lived unheralded in the Bronx for decades, initially cast off by black leaders who feared she was not the right face for their battle, according to a new book that has plucked her from obscurity.

Last week Phillip Hoose won the National Book Award for Young People’s Literature for “Claudette Colvin: Twice Toward Justice,” published by Farrar, Straus & Giroux. The honor sent the little-selling title shooting up 500 spots on Amazon.com’s sales list and immediately thrust Ms. Colvin, 70, back into the cultural conversation.

“Young people think Rosa Parks just sat down on a bus and ended segregation, but that wasn’t the case at all,” Ms. Colvin said in an animated interview at a diner near her apartment in the Parkchester section of the Bronx. “Maybe by telling my story — something I was afraid to do for a long time — kids will have a better understanding about what the civil rights movement was about.”

Ms. Colvin made her stand on March 2, 1955, and Mrs. Parks made hers on Dec. 1 that same year. Somehow, as Mrs. Parks became one of Time Magazine’s 100 most important people of the 20th century, and streets and schools were named after her, Ms. Colvin managed to let go of any bitterness. After Ms. Colvin was arrested, Mrs. Parks, a seasoned N.A.A.C.P. official, sometimes let her spend the night at her apartment. Ms. Colvin remembers her as a reserved but kindly woman who fixed her snacks of peanut butter on Ritz crackers.

“My mother told me to be quiet about what I did,” Ms. Colvin recalled. “She told me: ‘Let Rosa be the one. White people aren’t going to bother Rosa — her skin is lighter than yours and they like her.’ ”

Ms. Colvin said she came to terms with her “raw feelings” a long time ago. “I know in my heart that she was the right person,” she said of Mrs. Parks.

Ms. Colvin was riding the bus home from school when the driver demanded that she give up her seat for a middle-age white woman, even though three other seats in the row were empty, one beside Ms. Colvin and two across the aisle.

“If she sat down in the same row as me, it meant I was as good as her,” Ms. Colvin said.

Two police officers, one of them kicking her, dragged her backward off the bus and handcuffed her, according to the book. On the way to the police station, they took turns trying to guess her bra size.

At the time, the arrest was big news. Black leaders, among them Dr. King, jumped at the opportunity to use her case to fight segregation laws in court. “Negro Girl Found Guilty of Segregation Violation” was the headline in The Alabama Journal. The article said that Ms. Colvin, “a bespectacled, studious looking high school student,” accepted the ruling “with the same cool aloofness she had maintained” during the hearing.

As chronicled by Mr. Hoose, more than 100 letters of support arrived for Ms. Colvin — sent in care of Mrs. Rosa Parks, secretary of the Montgomery branch of the N.A.A.C.P.

But Ms. Colvin was ultimately passed over.

“They worried they couldn’t win with her,” Mr. Hoose said in an interview from his home in Portland, Me. “Words like ‘mouthy,’ ‘emotional’ and ‘feisty’ were used to describe her.”

Mrs. Parks, on the other hand, was considered “stolid, calm, unflappable,” he said. The final straw: Ms. Colvin became pregnant by a married man.

A second Montgomery teenager, Mary Louise Smith, was also arrested for refusing to give up her bus seat — after Ms. Colvin’s arrest but before Ms. Parks’s — and she was also deemed an unsuitable symbol for the movement partly because of rumors that her father had an alcohol problem.

Although Ms. Colvin quickly left Montgomery, she returned during the peak of the bus boycott that Mrs. Parks had subsequently sparked, and testified in federal court in Browder v. Gayle, the landmark case that effectively ended bus segregation.

“It’s an important reminder that crucial change is often ignited by very plain, unremarkable people who then disappear,” said David J. Garrow, a Pulitzer Prize-winning biographer of Dr. King.

Even Mrs. Parks was forgotten for the better part of 20 years, only re-emerging as a world-famous figure in the early 1970s after magazine articles and attention in several children’s books.

Ms. Colvin, who relies on a cane to steady herself, retired in 2004 after 35 years as a nurse’s aide at a Manhattan nursing home. She contributed to her own obscurity: after settling in New York, she never talked about how her arrest helped prompt the famous bus boycott.

“She continued to heed her mother’s advice, and worried that drawing attention to herself would result in the loss of her job. “I wasn’t going to take that chance,” she said.

So she settled into living an average life. She never married. The son she had in Montgomery died at age 37; a second son is an accountant in Atlanta. She watches television — “Who Wants to Be a Millionaire” is a favorite — and is a regular at the diner.

Ms. Colvin said she reads two newspapers every day to keep up on current events, chatting about recent Nobel Prize winners. She likes Chris Rock and Alicia Keys. Aretha Franklincould stand to lose a few pounds, but she wore a good hat to President Obama’sinauguration. Don’t get Ms. Colvin started on Sarah Palin.

She has fond memories of Dr. King. “He was just an average-looking fellow — it’s not like he was Kobe Bryant or anything,” she said, fluttering her eyelashes. “But when he opened his mouth he was like Charlton Heston playing Moses.”

Mr. Hoose said he stumbled across Ms. Colvin’s story while researching a previous book, “We Were There, Too! Young People in U.S. History.” Several sources told him to investigate what had almost become an urban myth: that a teenager had beaten Mrs. Parks to the punch in Montgomery.

He eventually tracked down Ms. Colvin, who has an unlisted telephone number. She refused to talk to Mr. Hoose for almost four years.

Mr. Hoose won over his reluctant subject over a long lunch at the diner. It was clear, he said, that she yearned to have her story told despite protests to the contrary. “It was easy to find the rebel girl inside of her,” he said.

One of her first questions: “Can you get it into schools?”

Visit our Honoring Our Past Pages