Timeline of Major League Baseball
The following is a timeline of franchise evolution in Major League Baseball. The histories of franchises in the National Association of Base Ball Players (NABBP), National Association of Professional Base Ball Players (NA), Union Association (UA), and American Association (AA) before they joined the National League are also included. The charter members of the American League had all been members of the minor league Western League prior to it becoming a competing major league.
The first line is the formation of the National League in 1876, and the second is the transformation of the American League to a major league in 1901. The third line is the beginning of the expansion era in 1961.