Benjamin Drew, a Boston abolitionist acting in cooperation with officers of the Canadian Anti-Slavery Society, visited various towns of Upper Canada around the middle 1850's, interviewing scores of refugees from the slave states and copying their words soon after they were spoken. For reasons of safety, he protected the identity of his informants and used fictitious names. There were about 30,000 Negroes at that time in Upper, Canada, mostly adults who had once been slaves. John P. Jewett, the prominent abolitionist-minded publisher of Boston who had unexpectedly reaped a fortune from printing Uncle Tom's Cabin in 1852, vouched for the integrity and intelligence of Drew.

The testimony tends to stress well-known gross abuses, but some of the ex-slaves offer fresh insights into the working of the plantation system.