The ruling in plessy v. Ferguson in 1896 established that

seperate but equal doctrine

Explanation:

Soon after the ruling in Plessy V. Ferguson, government officials obtain a legal ground to separate the usage of infrastructures between African American and white citizens.

In that time, African American citizens were forced to do things such as taking different schools away form white citizens, using public bathroom that is not used by white citizens, only taking Bus seat on the back while the front seats were reserved for white people, etc.