The significant court ruling that effectively invalidated Jim Crow laws in the southern United States was Brown v. Board of Education, decided in 1954 by the Supreme Court. This landmark case declared that racial segregation in public schools violated the Equal Protection Clause of the Fourteenth Amendment. By stating that "separate but equal" educational facilities are inherently unequal, the ruling laid the groundwork for the civil rights movement. It catalyzed efforts to dismantle segregation across all facets of society, contributing to a legal and cultural shift toward greater equality in the following decades.