Washington—Watching the great civil rights march on television in August 1963, I couldn't help but notice that hundreds carried signs with a strange legend at the top: "UAW Says." UAW was saying "Segregation Disunites the United States," and many other things insisting on equality.

This "UAW" was a very odd word to my 11-year-old self and I asked my dad who or what "U-awe," as I pronounced it, was. The letters, he explained, stood for the United Auto Workers union.

It was some years later when I learned about the heroic battles of the UAW, not only on behalf of those who worked in the great car plants but also for social and racial justice across our society. Walter Reuther, the gallant and resolutely practical egalitarian who led the union for many years, was one of Martin Luther King Jr.'s close allies.

Remembering that moment is bittersweet on a Labor Day when so many Americans are unemployed, when wages are stagnant or dropping, and when the labor movement itself is in stark decline.

Only 12.3 percent of American wage and salary workers belong to unions, according to the Bureau of Labor Statistics, down from a peak of about one-third of the work force in 1955. A movement historically associated with the brawny workers in auto, steel, rubber, construction, rail, and the ports now represents more employees in the public sector (7.9 million) than in the private sector (7.4 million).