This book is a narrative history of the thirty-year struggle to outlaw slavery, starting with the founding of the American Anti-Slavery Society in 1834 and extending until the abolition of slavery in the United States at the end of the Civil War.

The core of the book consists of two sections: 1) the 20-year political struggle to restrict slavery through a succession of anti-extensionist parties starting in 1840 with the founding of the Liberty Party, extending through the Free Soil Party (1848-54) and ending with Abraham Lincoln being elected president as a Republican on the same basic platform as the Liberty Party in 1844. 2) The struggle by abolitionists to use the outbreak of the Civil War as a chance to rid the country of slavery using the executive wartime powers of the presidency.