Thurgood Marshall played a pivotal role in the civil rights movement through litigation as the chief counsel for the NAACP. His most notable achievement was arguing the landmark case, Brown v. Board of Education, which resulted in the desegregation of public schools in the United States. Marshall's legal strategies effectively challenged racial discrimination, laying the groundwork for future civil rights advancements. His commitment to justice and equality ultimately led to his appointment as the first African American Supreme Court Justice, where he continued to champion civil rights issues.