Conversation so far:
What was the AFL?
The American Federation of Labor (AFL) was a national federation of labor unions in the United States founded in Columbus, Ohio.
What was the CIO?
The Congress of Industrial Organizations (CIO) was a federation of unions that organized workers in industrial unions in the United States and Canada from 1935 to 1955.

Question: When did the AFL and the CIO merge?
Self-contained rewrite: When did the AFL and the CIO merge?