What ruled that segregation was legal as long as facilities were equal?

The doctrine that ruled segregation was legal as long as facilities were equal is known as "separate but equal," established by the U.S. Supreme Court in the 1896 case Plessy v. Ferguson. This landmark decision upheld state laws that enforced racial segregation in public facilities, asserting that as long as the separate facilities for African Americans and whites were equal in quality, segregation did not violate the 14th Amendment's Equal Protection Clause. This principle was later challenged and ultimately overturned by the Brown v. Board of Education decision in 1954.