Rachel May's rich new book explores the far reach of slavery, from New England to the Caribbean, the role it played in the growth of mercantile America, and the bonds between the agrarian south and the industrial north in the antebellum era--all through the discovery of a remarkable quilt. While studying objects in a textile collection, May opened a veritable treasure-trove: a carefully folded, unfinished quilt made of 1830sera fabrics, its backing...