Almost from the passing of the Canada Act, however, runaway Negroes began to come to Upper Canada, fleeing from slavery; this influx increased and never ceased until the American Civil War gave its death blow to slavery in the United States. Hundreds of blacks thus obtained their freedom, some having been brought by their masters near to the international boundary and then clandestinely or by force effecting a passage; some coming from far to the South, guided by the North Star; many assisted by friends more or less secretly. The Underground Railroad was kept constantly running.[24] These refugees joined settlements with other people of color freeborn or freed in the western part of the Peninsula, in the counties of Essex and Kent and elsewhere.[25] Some of them settled in other parts of the province, either together or more usually sporadically.

At the time of the outbreak of the Civil War there were many thousands of black refugees in the province.[26] More than half of these were manumitted slaves who in consequence of unjust laws had been forced to leave their State. While some of such freedmen went to the Northern States, most came to Canada, some returning to the Northern States. The Negro refugees were superior to most of their race, for none but those with more than ordinary qualities could reach Canada.[27]

The masters of runaway slaves did not always remain quiet when their slave reached this province. Sometimes they followed him in an attempt to take him back. There are said to have been a few instances of actual kidnapping, a few of attempted kidnapping.[28] There have been cases in which criminal charges have been laid against escaped slaves, and their extradition sought, ostensibly to answer the criminal charges. It has always been the theory in this province that the governor has the power independently of statute or treaty to deliver up alien refugees charged with crime.[29] To make it clear, the Parliament of Upper Canada in 1833 passed an Act for the apprehension of fugitive offenders from foreign countries, and delivering them up to justice.[30] This provides that on the requisition of the executive of any foreign country the governor of the province on the advice of his executive council may deliver up any person in the province charged with "Murder, Forgery, Larceny or other crime which if committed within the Province would have been punishable with death, corporal punishment, the Pillory, whipping or confinement at hard labour." The person charged might be arrested and detained for inquiry. The Act was permissive only and the delivery up was at the discretion of the governor.

When this act was in force Solomon Mosely or Moseby, a Negro slave, came to the Province across the Niagara River from Buffalo which he had reached after many days' travel from Louisville, Kentucky. His master followed him and charged him with the larceny of a horse which the slave took to assist him in his flight. That he had taken the horse there was no doubt, and as little that after days of hard riding he had sold it. The Negro was arrested and placed in Niagara jail; a prima facie case was made out and an order sent for his extradition.

The people of color of the Niagara region made Mosely's case their own and determined to prevent his delivery up to the American authorities to be taken to the land of the free and the home of the brave, knowing that there for him to be brave meant torture and death, and that death alone could set him free. Under the leadership of Herbert Holmes, a yellow man,[31] a teacher and preacher, they lay around the jail night and day to the number of from two to four hundred to prevent the prisoner's delivery up. At length the deputy sheriff with a military guard brought out the unfortunate man shackled in a wagon from the jail yard, to go to the ferry across the Niagara River. Holmes and a man of color named Green grabbed the lines. Deputy Sheriff McLeod from his horse gave the order to fire and charge. One soldier shot Holmes dead and another bayoneted Green, so that he died almost at once. Mosely, who was very athletic, leaped from the wagon and made his escape. He went to Montreal and afterwards to England, finally returning to Niagara, where he was joined by his wife, who also escaped from slavery.

An inquest was held on the bodies of Holmes and Green. The jury found "justifiable homicide" in the case of Holmes; "whether justifiable or unjustifiable there was not sufficient evidence before the jury to decide" in the case of Green. The verdict in the case of Holmes was the only possible verdict on the admitted facts. Holmes was forcibly resisting an officer of the law in executing a legal order of the proper authority. In the case of Green the doubt arose from the uncertainty whether he was bayoneted while resisting the officers or after Mosely had made his escape. The evidence was conflicting and the fact has never been made quite clear. No proceedings were taken against the deputy sheriff; but a score or more of the people of color were arrested and placed in prison for a time. The troublous times of the Mackenzie Rebellion came on, the men of color were released, many of them joining a Negro militia company which took part in protecting the border.

The affair attracted much attention in the province and opinions differed. While there were exceptions on both sides, it may fairly be said that the conservative and government element reprobated the conduct of the blacks in the strongest terms, being as little fond of mob law as of slavery, and that the radicals, including the followers of Mackenzie, looked upon Holmes and Green as martyrs in the cause of liberty. That Holmes and Green and their fellows violated the law there is no doubt, but so did Oliver Cromwell, George Washington and John Brown. Every one must decide for himself whether the occasion justified in the courts of Heaven an act which must needs be condemned in the courts of earth.[32]

In 1842 the well-known Ashburton Treaty was concluded[33] between Britain and the United States. This by Article X provides that "the United States and Her Britannic Majesty shall, upon mutual requisitions ... deliver up to justice all persons ... charged with murder or assault with intent to commit murder, or piracy or arson or robbery or forgery or the utterance of forged paper.... Power was given to judges and other magistrates to issue warrants of arrest, to hear evidence and if "the evidence be deemed sufficient ... it shall be the duty of the ... judge or magistrate to certify the same to the proper executive authority that a warrant may issue for the surrender of such fugitive."

It will be seen that this treaty made two important changes so far as the United States was concerned: (1) It made it the duty of the executive to order extradition in a proper case and took away the discretion, (2) it gave the courts jurisdiction to determine whether a case was made out for extradition.[34] These changes made it more difficult in many instances for a refugee to escape: but as ever the courts were astute in finding reasons against the return of slaves.

The case of John Anderson is well known. He was born a slave in Missouri. As his master was Moses Burton, he was known as Jack Burton. He married a slave woman in Howard County, the property of one Brown. In 1853 Burton sold him to one McDonald living some thirty miles away and his new master took him to his plantation. In September, 1853, he was seen near the farm of Brown, when apparently he was visiting his wife. A neighbor, Seneca T. P. Diggs, became suspicious of him and questioned him. As his answers were not satisfactory he ordered his four Negro slaves to seize him, according to the law in the State of Missouri. The Negro fled, pursued by Diggs and his slaves. In his attempt to escape the fugitive stabbed Diggs in the breast and Diggs died in a few hours. Effecting his escape to this province, he was in 1860 apprehended in Brant County, where he had been living under the name of John Anderson, and three local justices of the peace committed him under the Ashburton Treaty. A writ of habeas corpus was granted by the Court of Queen's Bench at Toronto, under which the prisoner was brought before the Court of Michaelmas Term of 1860.