Rosa Parks’ grandmother warned that the young girl would be lynched before she was 20 if she continued to stand up to white people. Rather than such a grim end, the girl grew up to launch the civil rights movement by refusing to stand up. Ms. Parks, 92, died Monday in Detroit.

Rosa Parks was a 42-year-old seamstress on her way home from work in Montgomery, Ala., in December 1955 when she refused to give up her seat on a bus for a white man, as required by Jim Crow laws. She was jailed and fined $14. Her simple act of civil disobedience sparked a yearlong bus boycott, nearly bankrupting the transit system, and a larger civil rights movement.

Ms. Parks, who was active in the National Association for the Advancement of Colored People before her celebrated bus ride, said her fearlessness in challenging oppressors likely came from protecting her younger brother from bullies.

“The real reason of my not standing up was I felt that I had a right to be treated as any other passenger. We had endured that kind of treatment for too long,” she recalled in 1992.

Ms. Parks was not the first black woman arrested for refusing to give up a seat on the bus, but as a hard-working, church-going woman, she made a good example. Despite her husband’s concerns for her safety, she agreed

to be a plaintiff in a case challenging the bus segregation law.

The year before, the Supreme Court overturned school segregation in the landmark Brown v. Board of Education case. In November 1956, the court ruled that the Montgomery bus segregation was unconstitutional. Blacks were shot boarding buses and black churches were bombed after the court ruling. Ms. Parks and her husband, Raymond, were the target of death threats and moved to Detroit. She died just months before a 50th anniversary celebration was to be held in her honor in Montgomery.

Ms. Parks received numerous honors including the Presidential Medal of Freedom and the Congressional Gold Medal, the nation’s highest civilian honor.

“I truly believe that there’s a little bit of Rosa Parks in all Americans who have the courage to say enough is enough and stand up for what they believe in. She did such a small thing, but it was so courageous for her as a humble person to do,” New York Rep. Charles Rangel said after her death.

A half century later, when persecution and discrimination still exist, Ms. Parks’ greatest legacy is to encourage others to stand up for what is right as she did on the bus.