In a speech delivered last month at the Justice Department, Attorney General Eric Holder described America as "a nation of cowards" when it came to the subject of race. "If we're going to ever make progress," he explained, "we're going to have to have the guts, we have to have the determination, to be honest with each other."

Last week in Miami, Vice President Joe Biden squandered a perfect opportunity to follow Holder's advice. Speaking before the annual convention of the AFL-CIO, Biden repeatedly flattered the powerful labor organization, yet made no mention of the American Federation of Labor's notoriously racist past. For more than half a century, AFL unions routinely banned African Americans from membership, segregated the few blacks they did admit into inferior Jim Crow locals, and lobbied state and federal officials for discriminatory legal privileges. When the federal government began passing pro-union legislation during the 1930s, it was racist outfits like the AFL that reaped the benefits.

During the early decades of the 20th century, black economic success typically occurred in spite of organized labor—not because of it. As African Americans migrated from the rural South to the industrial North, they frequently secured jobs by working for lower wages than unionized whites or by serving as strikebreakers—"scabs"—when discriminatory white unions walked the picket line. Blacks gained a foothold in Chicago's massive meatpacking industry in 1894, for example, when unionized butchers joined the striking American Railway Union, a whites-only outfit led by future Socialist presidential candidate Eugene V. Debs.

As historian Paul Moreno notes in Black Americans and Organized Labor, strikebreaking and working for lower wages made good economic sense to both the bosses and their new black employees—regardless of racial discord between them. "Owners could be as prejudiced as, or even more prejudiced than, their workers," Moreno points out, "but there was a limit to how much they would be willing to pay for it." As a result, the packinghouses soon employed more blacks than any other industry in the city.

Which didn't exactly please the unions. As AFL chieftain Samuel Gompers declared in 1905: "If the colored man continues to lend himself to the work of tearing down what the white man has built up, a race hatred worse than any ever known before will result. Caucasian civilization will serve notice that its uplifting process is not to be interfered with in any such way."

But the worst was still to come. In 1927, an Alabama contractor named Algernon Blair transported a crew of black construction workers to Long Island, New York to help build a new Veteran's Bureau hospital. In response to the presence of "cheap" and "bootleg" labor in his district, Republican Rep. Robert Bacon introduced legislation that became the Davis-Bacon Act, which required all contractors working on federal projects worth over $2,000 to pay their workers the "prevailing wage"—which typically meant the union wage.

During Senate hearings on the bill, AFL president William Green testified in support, claiming that "colored labor is being brought in to demoralize wage rates." Emil Preiss, business manager of the New York branch of the International Brotherhood of Electrical Workers (a powerful AFL affiliate that banned blacks from its ranks) told the House that Blair's workers were "an undesirable element of people." The bill's co-sponsor, Republican Sen. James Davis of Pennsylvania, was an outspoken racist, who argued in 1925 that Congress must restrict immigration to "purify the national stream of life, to dry up the sources of hereditary poisoning, and to keep America sound at the core."

President Herbert Hoover signed Davis-Bacon into law in 1931, precisely as the federal government began a public works spending spree that lasted well beyond the Great Depression. As the legal scholar David Bernstein notes in his book Only One Place of Redress, "The only recourse African Americans had in a labor market dominated by exclusionary unions that demanded above-market wages was their willingness to work for less money than the unionists." Davis-Bacon nullified that advantage just when blacks needed it most.

New Deal labor laws had a similar impact. The National Industrial Recovery Act and its accompanying National Recovery Administration (NRA), in effect from 1933 until the Supreme Court unanimously struck them down in 1935, established the practice of mandatory collective bargaining, whereby a union selected by a majority of employees became the exclusive representative of all employees. Since African Americans were barred from most unions, the law drastically limited their economic options.

While many on the modern-day left celebrate such compulsory unionism (if not the racialist character of New Deal-era unions), black leaders at the time took a dimmer view. Sociologist and historian W.E.B. Du Bois (who is nobody's idea of a conservative) declared that, "the most sinister power that the NRA has reinforced is the American Federation of Labor." The Chicago Defender, arguably the country's most influential black newspaper at the time, decried the NRA as the "Negro Removal Act" and "Negro Run Around."

Shortly after the Court eliminated the NRA, Democratic New York Sen. Robert Wagner restored compulsory unionism via the National Labor Relations Act, or Wagner Act, which President Franklin Roosevelt happily signed into law. It's worth noting that Wagner's bill originally contained a clause forbidding union discrimination against blacks, but that clause was dropped at the insistence of the AFL, which then received state-sanctioned monopoly powers.

Indeed, it wasn't until the Civil Rights Movement and the imposition of federal anti-discrimination laws in the 1960s that the AFL and other racist unions finally changed their ways. But those reforms only came after black workers had suffered decades of exclusion and abuse at the hands of organized labor. Too bad Vice President Biden didn't have the guts to mention it.

Damon W. Root is an associate editor at Reason magazine.