Complex sentence: The first challenges to such state laws were overruled by US Supreme Court decisions that upheld state constitutions that effectively disfranchised many, and "Plessy v. Ferguson", which allowed racial segregation of public facilities.
Split into simpler sentences: The first challenges to such state laws were overruled by US Supreme Court decisions that upheld state constitutions that effectively disfranchised many. In "Plessy v. Ferguson", the US Supreme Court allowed racial segregation of public facilities.