It is interesting to note that one of the causes of the American Civil War (also known, perhaps more correctly, as the War Between the States) was the threat of slavery to the White working class in the North of the USA.

Lawrence R. Tenzer and A.D. Powell have produced research into this little-known subject.

"The institution of slavery had existed in every one of the Northern states throughout the colonial period and such slavery was not limited to black slavery. White political prisoners and petty criminals from Britain were sold and brought to the colonies as slaves. ...During the 1850s, the South's plan to nationalize slavery was merely to reintroduce it in the North where it had previously existed just 50 to 75 years earlier. With so many white partus slaves in the South to begin with, the idea of expanding slavery to include white laborers in the North moved slavery from a matter of color to a matter of class. Southern politicians frequently pointed out that the slavery in Greece and Rome was based on social status, not on color. They also called attention to the fact that the slavery in the Bible was not Negro slavery.

...Political materials for the presidential campaign of 1856 include references to the literal enslavement of white people and illustrate the extent to which the idea had developed.

...The famous Richmond Enquirer reference about slavery not depending on "difference of complexion" and the laws of the slave states justifying the holding of white men in bondage was cited along with this quote from a leading South Carolina newspaper: "Slavery is the natural and normal condition of the labouring man, whether WHITE or black."

...All of the talk during the campaign of 1856 about the South enslaving Northern whites took on profound meaning after the Dred Scott decision allowed slavery into the territories. Another Dred Scott decision would allow slavery into the free states of the North. In either case, free white labor would have to compete with slave labor and could not survive because the average daily wage of little more than a dollar would become 10¢ or 25¢. White laborers who fell into poverty could be sold into slavery for debt. As "The New 'Democratic' Doctrine" said, "All that the Northern white laborer requires is somebody to sell him when he falls into poverty." In his book, A Journey in the Back Country, Frederick Law Olmsted asserted, "Nothing in fact but the enslavement of labor at the North, could in the nature of things, give that security...to the capitalists of labor at the South." In a footnote, Olmsted quoted the Richmond Enquirer: "While it is far more obvious that negroes should be slaves than whites, ...the principle of slavery is itself right, and does not depend upon difference of complexion."

A series of speeches and dialogues which included references to white slavery took place in the Senate and in the House of Representatives in 1860 and give a sense for what Northern members of Congress wanted to express on the eve of the Civil War. Congressmen Henry Waldron of Michigan, Israel Washburn, Jr. of Maine, William Windom of Minnesota, and Senator James R. Doolittle of Wisconsin and Senators Charles Sumner and Henry Wilson of Massachusetts all mention George Fitzhugh by name. His quote from Sociology for the South pertaining to "slavery, black or white" and the Richmond Enquirer quote about slavery not depending on "difference of complexion" were repeated time and again, showing the concern Northern politicians had regarding the enslavement of white laborers.

... In 1859 Lincoln referred to Southern political power "trying to show that slavery existed in the Bible times by Divine ordinance....whenever you establish that Slavery was right by the Bible, it will occur that that Slavery was the Slavery of the white man - of men without reference to color." Lincoln's own campaign newspaper, the Rail Splitter, spoke of white slavery. An article entitled "Capital Should Own Labor" asked, "Whatever may be your opinion of Negro Slavery, do you think White Men should be made Slaves?" The same edition included this excerpt from a speech by Senator Benjamin F. Wade of Ohio: "Capital should own labor - referring not merely to the labor of the colored man, but to that of the white man as well!" A front-page article reminded readers, "It is not long since the Richmond Examiner, a leading Southern organ of the Democracy, said that the natural condition of the laboring classes of whatever color was slavery." Many articles in Lincoln's paper discussed the in-surmountable problem free labor would have in competing with slave labor, and the specter of white slavery was always present.

... When one truly understands that the politics of slavery had no regard for color, it becomes clear that free laborers in the North and others fought to abolish slavery, not out of altruism, but in order to insure freedom for themselves and their loved ones. Slavery black or white answers a major question that has puzzled historians of the American Civil War as to why Northern whites would fight to free blacks they believed to be an inferior race. Slavery black or white also begs the question as to whether or not the Civil War would have occurred if the existence of white slaves had not brought home to Northern citizens the great danger that slavery posed to their free society. The authors do not claim that white slavery was the only cause of the Civil War, but it was certainly an important cause which has been overlooked in academic literature."[91]