What wa the importance of the plessy v. ferguson (1896) decision by the supreme court

It was a milestone in the history of racial segregation. In 1896 the US Supreme Court took a decision that support the constitutionality of racial segregation in the time of  ¨separate but equal¨ doctrine. The case originated when an African-American train traveller refused to sit in a car for blacks. The Supreme court refused Plessy's argument stating  that a law that indicates a legal distinction between whites and blacks was not unconstitutional.    

worldwide, 780 million people do not have access to an improved water source. an estimated 2.5 billion people lack access to improved sanitation (more than 35% of the world's population)