Rosa Parks played a crucial role in the Montgomery Bus Boycott by refusing to give up her seat to a white passenger, an act of civil disobedience that sparked a significant movement against racial segregation. Her arrest on December 1, 1955, served as a catalyst for the boycott, which lasted over a year and aimed to end discriminatory bus practices in Montgomery, Alabama. Parks' actions highlighted the power of nonviolent resistance and galvanized support for the civil rights movement. Her bravery and commitment to justice ultimately contributed to significant legislative changes in the U.S.