In his soaring and moving speech on race this past spring in Philadelphia, Sen. Barack Obama eloquently spoke of how the U.S. Constitution, a document which purported to enshrine our new country's commitment to democracy, "was stained by this nation's original sin of slavery." The practice of slavery, and how it has marred our attempts to be truly a nation of, for and by the people, has never been fully confronted by our government or citizenry -- nor has it been fully eradicated.

What came to many of us as a revelation this year, presented by the Wall Street Journal's Douglas A. Blackmon in his book, "Slavery by Another Name," is that the enslavement of tens of thousands of black Americans in the South did not end in 1865 with the Union victory in the Civil War. Rather, the "peculiar institution" of slavery continued until 1945 and was exploited to fuel the United States' rapid and often destructive industrial growth.

As Mr. Blackmon explains, after the official end of slavery in 1865, southern political and industrial leaders found a loophole in the 13th Amendment, the anti-slavery amendment which forbids forced labor except when used as punishment for people convicted of criminal offenses. Exploiting this loophole, whites in the South who chafed at the newfound freedoms of African Americans and who continued to long for cheap or free labor, began to arrest blacks en masse on baseless charges, including the overly broad "crime" of vagrancy (i.e., standing around unoccupied), "offensive conduct," talking to white women or any other trumped-up offense they could come up with.

The targeted black citizen was then hauled before a judge or justice of the peace, pressured by implied threats of violence into confessing to a crime, and fined for both the crime and the "costs" incurred by the arresting officer, the judge and witnesses. The accused was then offered to an industrialist or farmer who offered to pay the exorbitant fines and costs in return for the accused signing a contract of indentured servitude by which he agreed to work for a certain period of time (for months or a year) to pay off his debt.

As it turned out, the accused black citizen would continue to incur "debts," thereby extending his servitude indefinitely -- many times until his death, which usually would come early as result of horrendous treatment, often worse than during antebellum times, often including daily beatings, overwork and starvation.

While this new twist on slavery continued in the South, it also was exploited by northern industrialists, particularly in the coal and steel industries, who wanted the cheap labor and a means to undercut growing attempts to unionize workers.

One of the largest users of forced labor was Pittsburgh-based U.S. Steel, which purchased a coal mine -- indeed, a slave mine -- from the Tennessee Coal, Iron & Railroad Co. at the beginning of the 20th century. U.S. Steel signed a lease with the state of Alabama to acquire hundreds of prisoners, almost all black and almost all arrested on absurd charges, who it put to work in its Alabama mine No. 12. The many laborers who died during their periods of servitude either were buried in unmarked graves or burned inside the mines.

As Mr. Blackmon notes in his book, U.S. Steel, unlike some companies that had used prison/slave labor during the late 19th and early 20th century, has never owned up to its crimes, much less paid compensation to the families of victims.

Mr. Blackmon's book ends in 1945 when this method of re-enslaving black Americans largely ended. The United States was shamed into cleaning up its act after its World War II enemies scored propaganda points by claiming that the United States had no grounds to complain about their enslavement of innocent prisoners when its was doing the same thing.

Unfortunately, the loophole in the 13th Amendment still allows for prison labor and it still is exploited.

The United States imprisons more of its citizens per capita than any nation in the world -- a total of 2 million -- and African Americans are imprisoned at rates far above their proportion of the population. U.S. corporations, such as IBM, TWA, Lee Jeans, Microsoft, Boeing and Victoria's Secret, to name a few, can employ these prisoners for far less than minimum wage, thereby exploiting the prisoners while taking good jobs away from workers outside the prison system. Meanwhile, those in prison, many of whom languish in captivity for small crimes such as petty drug offenses, are subject to brutal treatment, such as rape.

U.S. corporations continue to use slave labor of a more traditional kind, as well, in the even deeper south of Latin America and Africa. To cite just two examples:

It was revealed in 2004 that the largest steel producer in the United States, Nucor Corp., was using pig iron derived from charcoal that had been supplied from Amazonian plants which utilized slave labor. This steel, in turn, was used by U.S. auto manufacturers. As a Brazilian prosecutor who inspected the plants noted, "I saw cattle living in better conditions than the workers."

Similarly, the Firestone Tire and Rubber Co. was running a virtual slave plantation, including child laborers, at its giant Liberia rubber farm, which, until very recently, operated as a country unto itself.

Over the past several years the U.S. Justice Department has successfully prosecuted a number of slavery cases against growers in central Florida, as well. Growers in this area, some who remain at-large, supply vegetables to U.S. companies such as Burger King.

The point is this. As we celebrate the anniversary of our independence, we must honestly assess where we are as a nation, and whether and to what extent our nation's promise of freedom and democracy have been fully realized, including for people who may live outside the country but who nonetheless contribute to its growth and standard of living.