Thurgood Marshall played a significant role in the landmark case Brown v. Board of Education, which was pivotal in the fight against racial segregation in the United States. As the lead attorney for the NAACP Legal Defense Fund, he argued that segregated schools violated the Equal Protection Clause of the 14th Amendment. Marshall's compelling arguments, combined with extensive research and testimonies, ultimately led to the Supreme Court's unanimous decision in 1954 to declare segregation in public schools unconstitutional. This landmark case marked a crucial turning point in the American civil rights movement, promoting the integration of schools across the nation.