Uncle Tom’s Cabin Poster After Congress passed the Fugitive Slave Act in 1850, Harriet Beecher Stowe’s outraged sister-in-law told her, “Now Hattie, if I could use a pen as you can, I would write something that will make this whole nation feel what an accursed thing slavery is.” This poster advertising the novel Stowe wrote calls it “The Greatest Book of the Age.” The novel fueled the growing antislavery crusade. The Granger Collection, New York.