A fter slavery had been abolished in the British Empire, anti-slavery organizations in Britain, Canada and the United States focused their efforts on the eradication of slavery in the southern United States, the last large English-speaking slavocracy. American slavery was of some immediate concern to Canada because of the growing number of formerly enslaved as well as free-born Blacks immigrating primarily to Toronto and what is now southwestern Ontario. While some white settlers felt threatened by this new wave of immigrants, Canadian Abolitionists were inspired to action by a growing awareness of the human cost of slavery and of the racist laws aimed at inhibiting the growth of a free black community in the United States.

In 1837, the Upper Canada Anti-Slavery Society was created. As Canada's first major Abolitionist society, it drew members from Upper and Lower Canada and made contact with other Abolitionists in the U.S. and Britain. While this organization was relatively short-lived, passage of the punitive American Fugitive Slave Act in 1850 again galvanized Canadians into action. In 1851, the Canadian Anti-Slavery Society was established. The strength of this organization lay in the inter-racial collaboration between members of the Underground Railroad refugee community, establishment white supporters such as newspaper publisher George Brown, leaders of the Presbyterian Free Church and the Congregational Church, and many members of Toronto's growing business and professional elite.

With increasing numbers of refugees pouring into the province after 1850, the Underground Railroad refugee community and its supporters were kept busy trying to help the newcomers to establish themselves. The Canadian Anti-Slavery Society raised money for refugee relief and ran an adult night school that delivered agricultural training. It also fought extradition, opposed separate schools and sponsored eminent Abolitionist speakers. George Brown's newspaper, The Globe, was its mouthpiece. Many smaller papers, mostly owned and operated by Underground Railroad refugees, were also engaged in the Abolition movement, including Henry Bibb's Voice of the Fugitive, Mary Ann Shadd Cary's Provincial Freeman, Linton Stratford's The Voice of the Bondsman and the Reverend A.R. Green's The True Royalist and Weekly Intelligencer. George Brown's house in Toronto has been designated a national historic site because of its association with this staunch Abolitionist and Father of Confederation.