For more than half of the 20th century, the American South was a rigidly segregated society. Nowhere were segregation laws more entrenched than in the public schools. To fight those laws, Thurgood Marshall and the NAACP Legal Defense Fund took on a notorious 1896 Supreme Court decision called Plessy vs. Ferguson. An African American named Homer Plessy had challenged a Louisiana law requiring separate train cars for blacks and whites. The Supreme Court ruled against Plessy and cemented the devastating principle of "separate but equal," which allowed states to exclude black people from public places as long as they had access to equal, segregated facilities. In the era of Jim Crow, separate was rarely equal.