Answer: Harriet B. Stowe
Further detail:
Harriet Beecher Stowe's novel, Uncle Tom's Cabin, was hugely popular with abolitionists around the world. The book was the 2nd-best selling book of the 19th century -- coming in behind only the Bible (the perennial bestseller).
In response to Stowe's book, British women compiled a petition that got so many signatures it filled 26 leather bound volumes, in which they urged their sisters in America to keep up the fight to free the slaves. The impact of Stowe's book shows that what can be done fighting with the pen is just as mighty as what might be done with a sword!
