A book by Harriet Beecher Stowe, first serialized in 1850-1851. It had enormous effect in shaming complacent northerners to take arms against the practice of slavery. Many have called it the most influential book of the 19th century. Tolstoy likened it to Les Miserables and A Tale of Two Cities as a novel of morals.
These days, it's easy to forget what a success Uncle Tom's Cabin was in antebellum America. It went through 120 printings its first year, selling over 500,000 copies by 1857 - a record at the time. The book went on to be pubished in hundreds of editions, in all languages around the world and is still in print today. As a play, Uncle Tom's Cabin was in continuous production for 81 years from 1853 to 1934, making it the longest running play in American history (although Mrs. Stowe earned no royalties from the play or most foreign editions).
The popularity of the book contributed greatly to the success of antebellum anti-slavery fund raising. During a tour of Europe, Mrs Stowe was actually presented with caskets of gold from English, Scotch, Irish and French admirers of the book for her to take back and use in the anti-slavery cause.