There have been many moments of labor upsurge in America: the influx of members into the Knights of Labor in 1886, the dramatic growth of unions during and after World War I, and the great wave of public sector unionism in the 1960s and ‘70s. But none matches the period of the 1930s and ‘40s, when millions of workers unionized under the aegis of the great labor federation, the Congress of Industrial Organizations, or CIO. If we’re looking to get millions of private-sector workers into the labor movement today, there’s no better example than the ascendant period of the CIO.