Columbus claimed to have found a route to the West Indies (what he was looking for). He belived his claim until his death. However, it was later discovered that he had in fact found the Americas.
The McCarthy Era was one of great paranoia in the UN regarding Communism and its spread. Thousands of false accusations were made and people were detained for no reason.
We still think that direct exposure to filth/decay can give us diseases and it’s probably true.
In Plessy v. Ferguson, the Supreme Court ruled that facilities that were "separate but equal" were permissible under the US Constitution.
This allowed the Jim Crow laws to develop wherein African Americans went to different schools, ate at different restaurants or in different sections, and were generally segregated from the population
The answer is Black Death
