The National Association of Professional Base Ball Players, formed in March 1871, was the game’s first professional league. Any professional or semi-pro club could enter the NA pennant race simply by paying a $10 fee, and each club was responsible for scheduling its own games with the other contenders. Eight to thirteen clubs began each of the association’s five seasons, but each year one to six clubs failed to finish. Only three of the twenty-three clubs that competed in the NA played all five years: Mutual of New York, Athletic of Philadelphia (which won the first NA pennant), and Boston’s Red Stockings (who won the other four).
