Slavery had been a legal institution in the region of Indiana when it was controlled by France and Great Britain, and remained legal until 1787 when the Northwest Territory was organized by the United States of America. The Northwest Ordinance prohibited further expansion of slavery in the region, but allowed for the continuation of existing slave arrangements.
When the Indiana territory was established in 1800 many slaveholders immigrated to the territory bringing their slaves with them. The territory passed legislation that allowed for the slaves to be indentured within the territory. This law allowed slaveholders to continue in their ownership of slaves that were purchased outside of the state, even if the slaves came to reside in Indiana.
When Indiana was granted statehood in 1816 the constitution instituted a ban on slavery. This ban brought the previous laws that had permitted slavery into conflict, and the issues of whether preexisting slave arrangements were still legal was brought before the courts on several occasions. Each time the circuit courts had denied or approved the freedom of the slaves on a individual basis.
In 1819 two abolitionists, John Osborn and Amory Kinney, sought the aid of a Vincennes law office to test the legality of slave arrangements made prior to 1816. The two were Canadians who had immigrated to Indiana after the War of 1812. They believed that the constitutional ban on slavery extended to all slaves, including those held before 1816. The lawyers at the office, Colonel George McDonald and Moses Tabbs, also members of the anti-slavery party, began to prepare a test case to bring before the courts.
To ensure their case would have the widest reaching effects, they chose to attempt to free a slave name Polly who belonged to Hyacinthe Lassalle of Vincennes. The Lassalles were among the oldest family of immigrants in the state and had been in the region since France had owned it in the 18th century. Lassalle's father was a French trader who settled near Fort Wayne around 1765 where he married a Miami woman, and John was born to the couple in 1777. Polly had been purchased before the Northwest Territory had been established, and if she could be freed then a precedent would be set whereby all other slaves in the state could also be set free. The defense of Lassalle was performed by Judge Jacob Call, a future Congressman.
The case was first submitted to the circuit court in Vincennes where it was ruled that Polly should remain a slave. The court cited the fact that Polly was owned before the Northwest Ordinance was passed, and the wording of the Virginia Deed of Cession as proof, claiming that Lassalle's ownership of Polly was protected by federal law.
In June of 1820 the case was appealed to the Supreme Court of Indiana. Chief Justice Isaac Blackford was the son-in-law of McDonald, one of the plaintiff's lawyers. The plaintiff's lawyers argued that the constitution superseded all other laws, including one written prior to the constitution's adoption, and that the Northwest Ordinance ceased to apply to Indiana after statehood. The defense argued that the Northwest Ordinance, a federal law, superseded the state constitution and that it could only be repealed by the federal government, and because it was not repealed, it was still in effect regardless of Indiana's status in the Union. The court decided in favor of Polly and in the July decision court stated that
...the framers of our constitution intended a total and entire prohibition of slavery in this state. ...it follows, as an irresistible conclusion, that, under our present form of government, that slavery can have no exisitance in the State of Indiana, and, of course, that the claim of the said Lasselle cannot be supported.
The 1820 US census revealed that there where 190 slaves in Indiana and 1,200 free blacks, many of whom had been freed by the decision. The number of slaves dropped off dramatically and there were only three slaves in the state in both the 1830 and 1840 censuses.