Which event marked the beginning of segregation in professional baseball in the late 1800s? Congress passed a law segregating all sports. Branch Rickey fought for segregation before the Supreme Court. An executive order requiring segregation was issued. Baseball owners reached an informal agreement on segregation.

The correct answer is the last: "Baseball owners reached an informal agreement on segregation".

Segregation in baseball started in 1867 after the Pennsylvania Convention of Baseball that took place in Harrisburg. A team formed by African Americans, the Pythians, was not allowed to participate.

After that, there was a reaction in chain and many white players refused to play against teams with black players. In the end it was something generally accepted that black people were not playing in the National League.

The Correct Answer is "Baseball owners reached an informal agreement on segregation".

Explanation:

Jackie Robinson Crosses the Color line and becomes the first African American major league baseball player since the beginning of the Jim crow law.

Robinson broke the baseball color line when he started playing for the Brooklyn Dodger in April 1947.

The Dodgers mark the beginning of the end of color or racial segregation in professional baseball.