I say 1947 because that was the year the Truman Doctrine was announced. I think that's the official birthday of the red hunts that ensued. Much of that early red-hunting was targeted at the AFL-CIO, which still had a serious and vigorous left within it. This left was trying to reverse the labor right's trading of political independence for the acceptance of collective bargaining by big capital.
Also, I believe the 1947 AFL-CIO convention was a decisive battle, which the right, which invited Secretary of State Marshall to address the convention about the need for anti-communism, won.
My teacher and source on all this is my mentor, David Milton, who wrote _The Politcs of U.S. Labor_. The sell-out David documents has never even been discussed, let alone reversed, with the AFL-CIO.
BTW, David has a great new book on how British labor worked with Lincoln's ambassador to England to prevent British entry into the U.S. Civil War. It's called _Lincoln's Spymaster_. Great stuff!