Thirty years before Lincoln issued the Emancipation Proclamation, the antislavery movement won its first victory in the British Parliament. On August 1, 1834, the Abolition of Slavery Bill took effect, ending colonial slavery throughout the British Empire. Over the next three decades, "August First Day," also known as "West India Day" and "Emancipation Day," became the most important annual celebration of emancipation among people of African descent in the northern United States, the British Caribbean, Canada West, and the United Kingdom and played a critical role in popular mobilization against American slavery. In Rites of August First, J. R. Kerr-Ritchie provides the first detailed analysis of the origins, nature, and consequences of this important commemoration that helped to shape the age of Anglo-American emancipation.