"My parents were slaves in New York State. My master's sons-in-law ... came into the garden where my sister and I were playing among the currant bushes, tied their handkerchiefs over our mouths, carried us to a vessel, put us in the hold, and sailed up the river. I know not how far nor how long -- it was dark there all the time." Sophia Burthen's account of her arrival as an enslaved person into what is now Canada sometime in the late 18th century,...