January 1, 2013, marked the 150th anniversary of the Emancipation Proclamation. This revolutionary document ushered in the Thirteenth Amendment and the end of slavery in the United States. These two great legal documents were the culmination of a long struggle that began in the colonial period with the arrival of the first African slaves in North America. The Great Emancipation of the 1860s cannot be understood without studying what is often called the “first emancipation”—the growing belief among many...