Plessy v. Ferguson
The Supreme Court, in a 7-1 decision, ruled that the Louisiana law was valid.  They said that requiring whites and blacks to ride in separate trains did not harm blacks in any way.  Justice John Marshall Harlan was the only justice who thought the law was against the Constitution.  He thought segregation made black Americans feel inferior.  He said that the Constitution is "color blind" and that the law should not treat any group better than any other group.