In the summer of 1968, Jack Olson wrote a series for Sports Illustrated about race (it was later turned into a book). Here is the first piece: "The Black Athlete: A Shameful Story."

And from the article called "In the Back of the Bus":

Shortly before the St. Louis Cardinals' Bob Gibson took the mound recently to try to equal Don Drysdale's record of six consecutive shutouts he was asked if the pressure of the situation bothered him. "I face more pressure every day just being a Negro," he said.

"You know those junkyards along the highways in Jersey?" said Larry Doby, the first Negro ever to play in the American League. "Well, they have scrap heaps just like that for athletes—most of them black. Black athletes are cattle. They're raised, fed, sold and killed.... Baseball moved me toward the front of the bus, and it let me ride there as long as I could run. And then it told me to get off at the back door."

"Man, put that pen away," said Curt Flood of the Cardinals this spring when a Negro reporter began to ask him about race relations. "The next thing you know I'll be playing in Tulsa."

Gibson was bitingly serious, Doby deeply bitter and Flood only half kidding. Though all three are baseball players and the remarks of each were directed at a different aspect of the problem, all were answering the question of whether the professional Negro athlete is viewed as an equal—more or less. The pro sports establishment would maintain that it is a bastion of racial equality. But in spite of 20 years of progress, the professional entrepreneurs still prefer their Negroes in the back of the bus.

A few years ago, Deadspin had a post on Olson's series. Be sure to check it out.