Dred Scott was born a slave in Virginia between 1795 and 1800. In 1820, he followed his owners--Peter Blow--to Missouri. In 1832, Blow died and the next year U.S. Army Surgeon Dr. John Emerson purchased Scott. After purchasing Scott, Emerson took him to Fort Armstrong, which was located in Illinois. Illinois, a free state, had been free as a territory under the Northwest Ordinance of 1787, and had prohibited slavery in its constitution in 1819 when it was admitted as a state. Scott remained there until 1836.
In 1836, Scott was again relocated. This time he was taken to Fort Snelling, which was located in part of the Wisconsin territory. As a result, Scott was once again taken to a territory where slavery was “forever prohibited” by United State Congress under the Missouri Compromise. Moreover, two weeks before entering the Wisconsin territory, Congress passed the Wisconsin Enabling Act, effectively making slavery illegal in the Wisconsin territory under three distinct statues. First of all, the act mandated that the laws of Michigan, which was a free state, govern the new territory. Secondly, the Enabling Act made the Northwest Ordinance applicable in the territory, which also prohibited slavery. On top of all of this, the Wisconsin Enabling act reaffirmed and supplemented the Missouri Compromise. Thus, by taking Scott to this territory and keeping him there for two and a half years, Emerson was breaking the law in three distinct ways. This provided Scott with a legitimate basis on which to claim his freedom in court, although Scott did not act on this opportunity.
During his stay at Fort Snelling, Scott was legally married to Harriet Robinson, with the knowledge and consent of Emerson. This potentially provided Scott with an additional basis for claiming his freedom because under the laws of most southern states, a slave could never be legally married. This was so for three reasons. First, slaves could not enter legally binding contracts and marriage is a contract. Secondly, the legal recognition of marriage would undermine the property interest of the slaveholder. Finally, recognition of slave marriages could prompt slaves to demand and claim other rights, such as the right and duty to protect one’s wife from assault by others (including the slave owner). But once again, Scott made no attempt at his freedom.
In 1837, the Army ordered Emerson to Jefferson Barracks Military Post, south of St. Louis, Missouri. Emerson left Scott and Scott's wife Harriet at Fort Snelling, where Emerson rented them out for profit. By hiring Scott out in a free state, Emerson was effectively bringing the institution of slavery into a free state, which was a direct violation of the Missouri Compromise, the Northwest Ordinance, and the Wisconsin Enabling Act.
Before the end of the year, the Army reassigned Emerson to Fort Jessup, Louisiana. There Emerson married Eliza Irene Sanford in February 1838. Emerson then sent for Scott and Harriet, who proceeded to Louisiana to serve their master and his wife. While en route to Louisiana, Scott's daughter Eliza was born on a steamboat underway along the Mississippi River between the Iowa Territory and Illinois. Because Eliza was born in free territory, she was technically born as a free person under both federal and state laws.Moreover, upon entering Louisiana, the Scotts could have once again sued for their freedom, but did not. In all likelihood, the Scotts would have been granted their freedom by a Louisiana court, as Louisiana courts had previously granted slaves their freedom so long as it was shown that they had lived in a free state for a time.This was Louisiana state precedent for over 20 years.
Of course, it makes sense that the Scotts would not pursue their freedom in Louisiana: there is no reason to believe that they would be aware of this Louisiana state precedent. But it is curious that the Scotts made the trip to Louisiana at all: they made the trip down the Mississippi unsupervised and along the way they passed various free towns. The Scotts could have easily gotten off of the ship and taken their freedom. Once again though, they did not.
Toward the end of 1838, the Army again assigned Emerson to Fort Snelling. By 1840, Emerson's wife, Scott, and Harriet returned to St. Louis while Emerson served in the Seminole War. While in St. Louis, they were once again hired out and Emerson was once again breaking federal law. In 1842, Emerson left the Army. He died in the Iowa Territory in 1843; his widow Eliza inherited his estate, including Scott. For three years after Emerson’s death, the Scotts continued to work as hired slaves. In 1846, Dred attempted to purchase his and his family’s freedom, but Eliza Irene Emerson refused, prompting Dred to finally resort to legal recourse.