Here’s an excerpt from The Last Train to Cooperstown:

“Despite being kept out of white organized professional baseball, African American ballplayers had the opportunity to compete against white professional players. In the fall after the regular season ended, many white players would make extra money by forming teams to play exhibition games against Negro League players. The practice was called ‘barnstorming’ as the white and black teams would travel from city to city to play games. Because the black teams would win as many or even more times than the white ones, Major League executives tried unsuccessfully to discourage their players from barnstorming. Black players also competed against white Major Leaguers in the winter leagues that operated during November and December in the Caribbean and California.”