The Plessy v. Ferguson case ruled that segregation was legal. This greatly impacted African American communities because even though the principle "separate but equal" was deemed equal, it really wasn't at all. African American citizens often did not have the same opportunities and they had it more difficult than average white Americans.
This was overruled by the Brown v. Board case. This was started when a young African American girl had to walk over a mile to her school everyday, when there was a white school a couple blocks away. This gained a lot of attraction, as it is proof that "separate but equal" is not actually equal at all. After awhile, this case lead an end to segregation in school systems, and this eventually lead to an end to segregation in general and the overall integration of different races in society.
It was the completion of the Northern Pacific Railroad that mostly changed the feelings toward Chinese workers in Washington because the rail lines were so popular.
