The history of forced labor in the United States encompasses to all forms of unfree labor which have occurred within the present day borders of the United States through the modern era. "Unfree labor" is a generic or collective term for those work relations, in which people are employed against their will by the threat of destitution, detention, violence (including death), lawful compulsion, or other extreme hardship to themselves or to members of their families.
The arrival of the Europeans ushered in the Atlantic slave trade, where Africans were sold into chattel slavery into the Americas. It lasted from the 15th through 19th centuries and was the largest legal form of unfree labor in the history of the United States, reaching 4 million slaves at its height. Slavery and involuntary servitude were made illegal through the thirteenth amendment, except as punishment for a crime. However, unfree labor still existed legally in the form of the peonage system, especially in the New Mexico Territory, debt bondage, penal labor and convict leasing, and debt bondage such as the truck system, as well as many illegal forms of unfree labor, particularly sexual slavery.
Labor reforms in the 19th and 20th eventually outlawed many of these forms of labors. However, illegal unfree labor in the form of human trafficking continued to grow, and the economy continued to rely on unfree labor from abroad. Starting at the end of the 20th century, there became an increased public awareness of human trafficking. More anti-human trafficking groups began to form and anti-human trafficking laws began to be passed, though the extent of the laws and the implementation varies widely from state to state. The U.S. Justice Department estimates that 17,500 people are trafficked into the country every year, but the true figure could be higher, because of the large numbers of undocumented immigrants. Those being trafficked include young children, teenagers, men and women and can be domestic citizens or foreign nationals. According to the Department of State's statistics from 2000, there are approximately 244,000 American children and youth that are at risk for sex trafficking each year. Of these children and youth, 38,600 were originally runaways.
Traditions of Native American slavery.
Native American groups often enslaved war captives whom they primarily used for small-scale labor. Some, however, were used in ritual sacrifice. While little is known, there is little evidence that the slaveholders considered the slaves as racially inferior; they came from other Native American tribes and were casualties of war. Native Americans did not buy and sell captives in the pre-colonial era, although they sometimes exchanged enslaved individuals with other tribes in peace gestures or in exchange for redeeming their own members. The word "slave" may not accurately apply to such captive people. Most of these so-called Native American slaves tended to live on the fringes of Native American society and were slowly integrated into the tribe.
In many cases, new tribes adopted captives to replace warriors killed during a raid. Warrior captives were sometimes made to undergo ritual mutilation or torture that could end in death as part of a grief ritual for relatives slain in battle. Some Native Americans would cut off one foot of captives to keep them from running away. Others allowed enslaved male captives to marry the widows of slain husbands. The Creek, who engaged in this practice and had a matrilineal system, treated children born of slaves and Creek women as full members of their mothers' clans and of the tribe, as property and hereditary leadership passed through the maternal line. The children did not have slave status. More typically, tribes took women and children for captives for adoption, as they tended to adapt more easily into new ways.
Several tribes held captives as hostages for payment. Various tribes also practiced debt slavery or imposed slavery on tribal members who had committed crimes; full tribal status would be restored as the enslaved worked off their obligations to the tribal society. Other slave-owning tribes of North America included the Comanche of Texas, the Creek of Georgia; the fishing societies, such as the Yurok, who lived in Northern California; the Pawnee, and the Klamath.
When the Europeans made contact with the Native Americans, they began to participate in the slave trade. Native Americans, in their initial encounters with the Europeans, attempted to use their captives from enemy tribes as a “method of playing one tribe against another” in an unsuccessful game of divide and conquer.
The Haida and Tlingit who lived along southeast Alaska's coast were traditionally known as fierce warriors and slave-traders, raiding as far as California. In their society, slavery was hereditary after slaves were taken as prisoners of war. Among some Pacific Northwest tribes, as many as one-fourth of the population were slaves.
Legal chattel slavery.
By the time of the American Revolution (1775–1783), the status of slave had been institutionalized as a racial caste associated with African ancestry. When the United States Constitution was ratified in 1789, a relatively small number of free people of color were among the voting citizens. During and immediately following the Revolutionary War, abolitionist laws were passed in most Northern states and a movement developed to abolish slavery. Most of these states had a higher proportion of free labor than in the South and economies based on different industries. They abolished slavery by the end of the 18th century, some with gradual systems that kept adults as slaves for two decades. But the rapid expansion of the cotton industry in the Deep South after the invention of the cotton gin, greatly increased demand for slave labor, and the Southern states continued as slave societies. They attempted to extend slavery into the new Western territories in order to keep their share of political power in the nation; Southern leaders dreamed of annexing Cuba to be used as a slave territory. The United States was polarized over the issue of slavery, represented by the slave and free states divided by the Mason–Dixon line, which separated free Pennsylvania from slave Maryland and Delaware.
Congress under Thomas Jefferson prohibited the importation of slaves, effective in 1808, but illegal smuggling took place. Domestic slave trading, however, continued at a rapid pace, driven by labor demands from the development of cotton plantations in the Deep South. More than one million slaves were sold from the Upper South, which had a surplus of labor, and taken to the Deep South in a forced migration, splitting up many families. New communities of African-American culture were developed in the Deep South, and the total slave population in the South eventually reached 4 million before liberation.
As the West was developed for settlement, the Southern states wanted to keep a balance between the number of slave and free states, in order to maintain a political balance of power in Congress. The new territories acquired from Britain, France, and Mexico were the subject of major political compromises. By 1850, the newly rich cotton-growing South was threatening to secede from the Union, and tensions continued to rise. With Southern church ministers having adapted to supporting slavery, as modified by Christian paternalism, the largest denominations, the Baptist, Methodist and Presbyterian churches split over the issue into regional organizations of the North and South. When Abraham Lincoln won the 1860 election on a platform of no new slave states, the South broke away to form the Confederacy; the first six states to secede held the greatest number of slaves in the South. This marked the start of the Civil War, which caused a huge disruption of the slave economy, with many slaves either escaping or being liberated by the Union armies. Due to Union measures such as the Confiscation Acts and Emancipation Proclamation in 1863, the war effectively ended slavery, even before ratification of the Thirteenth Amendment in December 1865 formally ended the legal institution throughout the United States.
Other forms of unfree labor.
Continued forms of involuntary servitude persisted after the Emancipation Proclamation and the adoption of the Thirteenth Amendment to the United States Constitution. This took place in various forms. The primary forms included convict leasing, peonage, and sharecropping, with the latter eventually encompassing poor whites as well and by the 1930s, they made up the vast majority. 
Black Codes.
The Black Codes were laws passed by Southern states in 1865 and 1866, after the Civil War. These laws had the intent and the effect of restricting African Americans' freedom, and of compelling them to work in a labor economy based on low wages or debt. Black Codes were part of a larger pattern of Southern whites trying to suppress the new freedom of emancipated African American slaves, the freedmen.
In the first two years after the Civil War, white dominated southern legislatures passed Black Codes modeled after the earlier slave codes. They were particularly concerned with controlling movement and labor, as slavery had given way to a free labor system. Although freedmen had been emancipated, their lives were greatly restricted by the black codes.
The term "Black Codes" was given by "negro leaders and the Republican organs", according to historian John S. Reynolds. The defining feature of the Black Codes was broad vagrancy law, which allowed local authorities to arrest freed people for minor infractions and commit them to involuntary labor.
Convict leasing.
With emancipation a legal reality, white Southerners were concerned with both controlling the newly freed slaves and keeping them in the labor force at the lowest level. The system of convict leasing began during Reconstruction and was fully implemented in the 1880s and officially ending in the last state, Alabama, in 1928. It persisted in various forms until it was abolished in 1942 by President Franklin D. Roosevelt during World War II, several months after the attack on Pearl Harbor involved the U.S. in the conflict. This system allowed private contractors to purchase the services of convicts from the state or local governments for a specific time period. African Americans, due to "vigorous and selective enforcement of laws and discriminatory sentencing", made up the vast majority of the convicts leased. Writer Douglas A. Blackmon writes of the system:
 ;templatestyles src="Template:Blockquote/styles.css" / ;It was a form of bondage distinctly different from that of the antebellum South in that for most men, and the relatively few women drawn in, this slavery did not last a lifetime and did not automatically extend from one generation to the next. But it was nonetheless slavery – a system in which armies of free men, guilty of no crimes and entitled by law to freedom, were compelled to labor without compensation, were repeatedly bought and sold, and were forced to do the bidding of white masters through the regular application of extraordinary physical coercion.
The constitutional basis for convict leasing is that the Thirteenth Amendment, while abolishing slavery and involuntary servitude generally, expressly permits it as a punishment for crime.
Peonage.
Peonage is a type of involuntary servitude. After the American Civil War of 1861–1865, peonage developed in the Southern United States. Poor white farmers and formerly enslaved African Americans known as freedmen who could not afford their own land would farm another person's land, exchanging labor for a share of the crops. This was called sharecropping and initially the benefits were mutual. The land owner would pay for the seeds and tools in exchange for a percentage of the money earned from the crop and a portion of the crop. As time passed, many landowners began to abuse this system. The landowner would force the tenant farmer or sharecropper to buy seeds and tools from the land owner’s store, which often had inflated prices. As sharecroppers were often illiterate, they had to depend on the books and accounting by the landowner and his staff. Other tactics included debiting expenses against the sharecropper's profits after the crop was harvested and "miscalculating" the net profit from the harvest, thereby keeping the sharecropper in perpetual debt to the landowner. Since the tenant farmers could not offset the costs, they were forced into involuntary labor due to the debts they owed the land owner.
After the Civil War, the Thirteenth Amendment prohibited involuntary servitude such as peonage for all but convicted criminals. Congress also passed various laws to protect the constitutional rights of Southern blacks, making those who violated such rights by conspiracy, by trespass, or in disguise, guilty of an offence punishable by ten years in prison and civil disability.