Fugitive slave laws provided slaveowners and their agents with the legal right to reclaim runaways from other jurisdictions. Those states or jurisdictions were required to deliver the fugitives. As early as 1643, the United Colonies of New England had required the return of runaways, and, after the American Revolution (1775–1783), the Northwest Ordinance of 1787 contained similar protections for slaveowners.included a Fugitive Slave Clause, which was agreed to without dissent at the Constitutional Convention. Following a dispute between Pennsylvania and Virginia, Congress passed the , which clarified the processes by which slaveowners could claim their property and was designed to balance the competing interests of free and slave states. In 1823, the law was upheld by Massachusetts in a case regarding a Virginia runaway, and then upheld again by the U.S. Supreme Court in 1842. The expanded the number of federal officials empowered to act in fugitive-slave cases, but by this time, public opinion, at least in antislavery hotbeds such as Boston, Massachusetts, had turned against such laws. Thus a captured Virginia slave named was rescued in 1851 and spirited north to Canada, but in 1854, authorities foiled an attempted rescue of the Virginia runaway slave . Compromise soon became impossible, and enforcement of the law effectively ended with the onset of the (1861–1865).