Who said, "So you're the little woman who wrote the book that started this Great War!"?

It is generally believed that Abraham Lincoln said to Harriet Beecher Stowe: "So you're the little woman who wrote the book that started this Great War!"  Stowe's family members claimed that Lincoln said those words to her when they met for the first time in 1862.

Harriet Beecher Stowe wrote Uncle Tom's Cabin about a decade prior.  It became immensely popular.  An abolitionist, she wanted to shine light on the evils of slavery.  Stowe had lost her toddler son to sickness, and this also served as a motivation for writing the story.  She felt that this tragic loss helped her to relate to slave mothers who were forcibly separated from their young children.

After the publication of Uncle Tom's Cabin, those who defended slavery protested and complained that the book contained exaggerations.  It added further tensions to an already divided nation, which explains Lincoln's alleged comment to Stowe.