Shirley J. Yee "Cary, Mary Ann Camberton Shadd," American National Biography Online, February 2000, http://www.anb.org/articles/09/09-00875.html.
Mary Ann Shadd continued her family's activist tradition by devoting her life to the advancement of black education and the immediate abolition of slavery. As a youth she attended a private Quaker school for blacks taught by whites, in which several of her teachers were abolitionists. During the 1840s she taught in schools for blacks in Wilmington, West Chester, New York City, and Norristown, Pennsylvania. When passage of the Fugitive Slave Act of 1850 endangered the freedom of free blacks as well as fugitive slaves, Shadd joined the faction of black abolitionists who promoted the controversial cause of voluntary black emigration to Canada. This movement illustrated the depth of disillusionment with the United States that had developed among many blacks since the 1840s. Angered and disappointed in the continued tolerance of slavery and the upsurge of violence against free blacks, a faction of black activists broke from the American abolitionist organization and from those black abolitionists who preferred to stay and fight oppression in the United States.
Between 1850 and 1860 approximately 40,000 blacks fled to southern Ontario. Shadd found employment in 1851 as a teacher of blacks in Windsor, Ontario, and was later joined by several members of her family. Shadd taught school and became a fervent spokeswoman for the emigration movement. Like most teachers in the black settlements, she had to struggle to keep her schools open, facing such obstacles as inadequate supplies, ramshackle school buildings, inclement weather, and the frequent outbreak of cholera and measles.