What was the rationale behind Plessy v. Ferguson decision of 1896?

Plessy v. Ferguson, 163 U. S. 537 (1896), was a landmark decision of the U. S. Supreme Court that upheld the constitutionality of racial segregation laws for public facilities as long as the segregated facilities were equal in quality

Plessy v. Ferguson, 163 U. S. 537 (1896), was a landmark decision of the U. S. Supreme Court that upheld the constitutionality of racial segregation laws for public facilities as long as the segregated facilities were equal in quality - a doctrine that came to be known as "separate but equal".