Professionalism

The NABBP permitted professional play beginning in 1869. The Boston Red Stockings and the Boston Baseball Club were founded in 1871. The NABBP split into two groups. The National Association of Professional Base Ball Players eventually developed into the National League.

Competitive Professional Baseball
Competitive Professional Baseball

Other competitive professional leagues formed and were disbanded regularly, until the American League declared in 1901 the intent to operate as a Major League.

The National League and the American League agreed about playing the World Series between the two champions starting 1903.