The United States was not the only nation to experience emancipation in the nineteenth century. Neither plantation slavery nor abolition were unique … - Eric Foner

History, however, is not a linear narrative of progress. Rights may be won and taken away; gains are never complete or uncontested, and popular movements generate their own countervailing pressures.

Lincoln asked the nation to confront unblinkingly the legacy of slavery. What were the requirements of justice in the face of this reality? What would be necessary to enable former slaves and their descendants to enjoy fully the pursuit of happiness? Lincoln did not live to provide an answer. A century and a half later, we have yet to do so.

Even as the United States has risen to become the predominant international power, however, conflict has persisted over the nature of American society itself and what its role in the world should be.