High Quality Content by WIKIPEDIA articles! The American Federation of Labor and Congress of Industrial Organizations (AFL–CIO) is a national trade union center, the largest federation of unions in the United States, made up of fifty-six national and international unions, together representing more than 11 million workers (as of June 2008, the most recent official statistic). It was formed in 1955 when the AFL and the CIO merged after a long estrangement. From 1955 until 2005, the AFL–CIO`s member unions represented nearly all unionized workers in the United States. Several large unions split away from AFL–CIO and formed the rival Change to Win Federation in 2005. The largest union currently in the AFL–CIO is the American Federation of State, County and Municipal Employees (AFSCME), with more than a million members.