What was the main argument of plessy v. Ferguson?

The main argument in Plessy v. Ferguson (1896) centered on the legality of racial segregation under the "separate but equal" doctrine. Homer Plessy, who was one-eighth Black, challenged Louisiana's segregation laws after being arrested for sitting in a whites-only train car. The Supreme Court upheld the state's law, asserting that racial segregation did not violate the Equal Protection Clause of the 14th Amendment, as long as the separate facilities were equal in quality. This decision institutionalized racial segregation and discrimination in the United States for decades.