Considering Baltimore and Philadelphia as part of a larger, Mid-Atlantic borderland, The Politics of Black Citizenship shows that the antebellum effort to secure the rights of American citizenship was central to black politics-it was an effort that sought to exploit the ambiguities of citizenship and negotiate the complex national, state, and local politics in which that concept was determined. In the early nineteenth century, Baltimore and Philadelphia contained the largest two free black populations in the country, separated by a mere hundred miles. The counties that lie between them also contained large and vibrant free black populations in this period. In 1780, Pennsylvania had begun the process of outlawing slavery, while Maryland would cling desperately to the institution until the Civil War, and so these were also cities separated by the legal boundary between freedom and slavery. Despite the fact that slavery thrived in parts of the state of Maryland, in Baltimore the free black population outnumbered the enslaved so that on the eve of the Civil War there were ten times as many free blacks in the city of Baltimore as there were slaves. While free blacks in both cities found that their legal rights were tenuous, African Americans could not ignore the possible protections the law afforded them. While they employed diverse tactics in defense of their liberties (for example, physical violence and the building of autonomous black institutions), African Americans recognized the importance of public policy and of the political struggles that helped to shape it.