Black players in organized white baseball in the pre-integration era - Beyond the Box Score
Athletes and activism: The long, defiant history of sports protests
On Jackie Robinson Day, remember the Black men who played in the majors before he broke the color barrier
Moses Fleetwood Walker was the first African American to play pro baseball, six decades before Jackie Robinson
Play Ball! Paving the way for Jackie Robinson National Museum of African American History and Culture
Magnificent Moses Fleetwood Walker Imperial Cabinet Photograph With Accompanying Action Photo (2)
Out at Home: Baseball Draws the Color Line, 1887 – Society for American Baseball Research
Why did some MLB players refuse to meet with Jackie Robinson when he first came into the league? - Quora
Pre-Negro Leagues stars laid the foundation for integration
Jackie Robinson becomes first African American player in Major League Baseball, April 15, 1947
Jackie Robinson Day: 2022 edition