Introduction

The transatlantic antislavery movement was, at its core, a network phenomenon. Abolitionists on both sides of the Atlantic coordinated campaigns, shared intelligence about the slave trade, and built coalitions through sustained correspondence. Yet most historical accounts treat the British and American movements as parallel but separate stories.

This study reconstructs the communication network of transatlantic abolitionism using a corpus of 12,000 letters drawn from 47 archival collections. By applying social network analysis, we can identify the key brokers who connected national movements, trace the diffusion of tactical innovations, and reveal the structural vulnerabilities that periodic crises exposed.

Data and Methods

Corpus Assembly

Letters were drawn from published correspondence collections, digitized archives, and manuscript repositories across Britain, the United States, and Jamaica. Each letter was coded for sender, recipient, date, origin city, destination city, and broad topic (legislation, tactics, fundraising, personal, theology).

Network Modeling

The correspondence network was modeled as a weighted, undirected graph where nodes represent individuals and edge weights represent the number of letters exchanged. Temporal snapshots were created at five-year intervals from 1790 to 1860.

Key Metrics

We calculated degree centrality (number of correspondents), betweenness centrality (brokerage potential), and eigenvector centrality (connection to other well-connected individuals). Community detection identified clusters of closely connected correspondents.

Results

Network Structure

The full network contains 847 individuals connected by 3,214 letter-exchange relationships. The network exhibits classic small-world properties: the average path length between any two correspondents is 3.4 steps, despite the geographic span of the network.

Brokers

Thomas Clarkson occupied the highest betweenness centrality in the early period (1790-1810), serving as the primary conduit between British parliamentary abolitionists and American Quaker networks. After 1830, Frederick Douglass assumed an analogous brokerage role, connecting the American Anti-Slavery Society with British radicals.

Crisis Vulnerability

The network was structurally vulnerable to the removal of key brokers. Simulated removal of the top five betweenness-centrality nodes increased average path length by 62%, suggesting that the movement depended heavily on a small number of transatlantic connectors.

Discussion

The network structure of transatlantic abolitionism reveals a movement that was simultaneously robust and fragile. The small-world topology enabled rapid information diffusion across the Atlantic, but the dependence on a handful of brokers created strategic vulnerabilities.

References

Blackburn, R. (2011). The American Crucible: Slavery, Emancipation and Human Rights. London: Verso.
Brown, C.L. (2006). Moral Capital: Foundations of British Abolitionism. Chapel Hill: UNC Press.
McCarthy, T. (2012). "The Networked Abolition Movement." Journal of Interdisciplinary History 43(2): 187-216.

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