Jackie Robinson's importance to sport and society is enormous. But when this site Eyewitness to History states that Jackie Robinson was the "first Black player in major league baseball", it is incorrect. As this site from the Library of Congress notes, there were Black players in the 19th century. Jackie Robinson broke "baseball's color barrier", as the Baseball Hall of Fame put it, but it was a wall that was once down, then rebuilt.
Wikipedia writes that Robinson "became the first African American Major League Baseball player of the modern era in 1947", and that would be correct, the "modern era" usually referring to the advent of the American League in 1901. However, Wikipedia's list of first black Major League Baseball players by team and date would be more accurate if it indicated "since 1900" or another qualifying term.
This in no way meant to dimishish the contribution made by and courage shown by Jackie Robinson.
(CREDIT: "Jackie Robinson comic book." Greenwich, CT: Fawcett Publications, July 1951. Vol. 1, no. 5. By Popular Demand: Jackie Robinson and Other Baseball Highlights, 1860s-1960s, Library of Congress. )