During the Cuban War of Independence (1868-1898) and U.S. Reconstruction, U.S. and Cuban Afro-descendants transformed regional commercial networks and port cities on the coast of the Gulf of Mexico, which had traditionally sustained Caribbean plantation economies, into an infrastructure for spreading radical interpretations of freedom and citizenship after slavery. My dissertation project examines the circulation of people and vernacular ideologies of race and citizenship between two societies transitioning from slavery to freedom. I hypothesize that, through labor unions, associational politics, and journalism, geographically mobile U.S. Reconstruction-era activists, along with Cuban journalists, artisans, union leaders, and anti-Spanish conspirators, collaboratively defined citizenship as membership of both national and trans-American communities of political belonging. As an idiosyncratic crossroads of French, Spanish, British, and U.S. political traditions and racial ideologies that mid-nineteenth century activist Afro-descendants drew upon, the Gulf’s revolutionary networks offer a case-study through which we can explore (1) the dynamic relationship between vernacular and formal-constitutional meanings of citizenship rights after the abolition of slavery; (2) the circulation of ideologies of rights across legal jurisdictions and political and cultural boundaries; and (3) the emergence of visions of diaspora in the Western Hemisphere. My research draws on rich, but underutilized primary sources located in U.S., Spanish, and Cuban archives, including notarial records, census data, embarkation and disembarkation records, journalism, personal and official correspondence, minutes of association meetings, consular reports, and judicial cases brought against alleged conspirators against the Spanish Crown.