Why did the AL expand first?

[Ubiquitous]

AL Expansion

as well as a SABR presentation

1961 AL Expansion

[dgarza]

and also given that the NL had had more westward movement? Was there concern that AL teams would move west if there was no expansion?

Might not have there been a concern that the AL wouldn't move west? I would think Baseball would have wanted AL teams in the West.

[brett]

I am interested in the 60s expansions. Is there a particular reason why the AL got to expand first? Did the 2 leagues both have to agree? Were players made available to be drafted across the majors? How many could you protect? Why the AL first when it was far less integrated, and also given that the NL had had more westward movement? Was there concern that AL teams would move west if there was no expansion?