What events took place that made Americans begin to question the idea of slavery and its inhumane nature?
There's an old story, almost certainly apocryphal, where President Lincoln meets with Harriet Beecher Stowe at a White House reception at the start of the Civil War and says to her
So this is the little lady who started this great war.
It's a nice story, but it's almost certainly not true. Nevertheless, it does contain a kernel of truth. The book that Harriet Beecher Stowe wrote, Uncle Tom's Cabin, played no small part in generating revulsion for the institution of slavery among millions of Americans, thus helping to precipitate the Civil War. The book, a powerful, searing indictment of the evils of slavery, became an instant best-seller, not just in the United States but all over the world. And most people who read the book became convinced that slavery was an evil that must be abolished.
a work of fiction,Uncle Tom's Cabin was based on the real-life experiences of actual slaves. This made Stowe's savage indictment of slavery all the more effective, as her readers could be sure that this was the kind of thing that was actually going on in their own country, not some remote, uncivilized corner of the globe.
After the book was published, many Americans, some of them for the first time, became acquainted with the horrific details of slavery as it was actually practiced. And what they found within the book's pages appalled them. Not every reader became an outright abolitionist, but at the very least Stowe had successfully roused the consciences of millions of Americans, turning them into implacable foes of an evil, morally degrading system.