The event that occurred first among the options listed is:
A. Homer Plessy sat in a train car for white people only.
This event took place in 1892 and was part of the Plessy v. Ferguson case, which upheld the legality of racial segregation. The other events occurred later: Rosa Parks' refusal was in 1955, the Supreme Court ruling in Brown v. Board of Education was in 1954, and the Jim Crow era generally is considered to have ended in the 1960s with the Civil Rights Movement.