The significant response to Rosa Parks' refusal to give up her seat in 1955 was the Montgomery Bus Boycott, a pivotal event in the American civil rights movement. Parks' arrest for defying segregation laws sparked a mass protest led by figures like Martin Luther King Jr. The boycott lasted for over a year, during which African Americans refused to use the city’s buses, significantly impacting the bus system's finances. The boycott raised awareness of racial injustice and led to a Supreme Court ruling declaring segregation on public buses unconstitutional, marking a crucial victory in the fight for civil rights.