In May 2019, it was widely reported that the wreck of the transatlantic slave ship, Clotilda, had been discovered in the Mobile-Tensaw River Delta, just north of the city of Mobile in Alabama. The Clotilda has long been thought to be the last transatlantic slaving ship to have arrived in the American South. It had lain in the mud since 1860. After 124 captive Africans had disembarked, illegal traffickers sailed away into the night and torched the vessel to cover their backs. The location of the wrecked vessel confirmed concretely for today's descendants of the Clotilda's African captives what they have always known but which had long been questioned. Widespread reporting of the discovery also further interrupted the dominant American national narrative that has hitherto remembered the role of the United States in the transatlantic trafficking of African lives as closing with the federal ban of 1808.

W.E.B. Du Bois detailed the ineffectiveness of the 1808 Act Prohibiting Importation of Slaves in his The Suppression of the African Slave-trade to the United States in 1894. His classic study was published less than forty years after the Clotilda arrived in Alabama, however, it is only recently that historians have increasingly turned their attention to the ways in which the transatlantic slave trade continued to flourish during the nineteenth century. The Last Slave Ships makes a major contribution to the scholarly field. As Harris notes, early on in his fine study, nearly four million Africans were forced aboard slave ships between the beginning of the century and the early 1860s, about one third of all captives who endured the Middle Passage crossing (p. 3). The trafficking of captive Africans bound for the plantations in the Americas had been outlawed by all nations by 1836 but it nevertheless continued albeit re-shaped and muddied by successive bans, treaties, and prohibitive penalties. During this “illegal” period, the promise of huge profits, various efforts at maritime suppression – notably by Britain – and the geopolitical chauvinism of the United States, helped to shape the murky contours of an often ambiguous, and ambivalently policed, maritime trade in captive African peoples.

The fate of the Clotilda bookends The Last Slave Ships and the study focuses on the closing decade of this criminal enterprise, by which time international suppression efforts had dispersed the Atlantic-wide community of slavers. The study does not focus on the sporadic arrival of slave ships in the American South, however, but on the formation of a “final triangle” connecting the coasts of Angola to the slave markets of Cuba via the burgeoning mid-century metropolis of New York. Here, during the early 1850s, a group of displaced human traffickers, mostly from Brazil, West Central Africa, and Portugal, were able to revive their business even though the United States had outlawed the trade nearly half a century earlier and then made it a capital offence in 1820. Taking up residence in the streets of what is today known as the Financial District in lower Manhattan, an international cartel – that came to be known as the Portuguese Company – prospered for a decade, mingled within the wider mercantile community. It was from their base in Gotham that they financed, outfitted, and dispatched American-built ocean-going slaving ships for the coasts of West Central Africa and to supply enslaved labour for the booming sugar plantations of Cuba. New York's booming port provided ideal cover for the criminal operation along with the corruption of its authorities and the availability of many willing hands. They were enabled by a ruling Democratic party with a zealous commitment to free trade and little investment in slave trade suppression.

Given the illicit nature of the international enterprise, the slave traders destroyed paper evidence of their transactions, disposed of vessels once voyages were complete, and quickly laundered their bloody profits. It is extremely difficult to find historical evidence of purposefully clandestine business practices. Nevertheless, Harris paints a vivid picture of their transnational racketeering by piecing together archival remains from collections in Spain, Portugal, Cuba, Great Britain, and the United States. He mines meticulously fragments of correspondence and financial accounts confiscated by British and Brazilian naval officers from intercepted vessels, slave traders’ documents recovered in Angola, and reports written by Spanish diplomats stationed in Washington, D.C. and Havana. He also focuses his analysis on secret dispatches written by informants hired by the British and American governments to spy on the traffickers in New York and Lisbon (pp. 57–58). Knitting together these rich sources, Harris provides a compelling and detailed account of how the traffickers raised and circulated capital, purchased American built vessels, dealt with the people merchants on the coasts of Africa, and how they sold captives in Havana. Acknowledgment of the modernity that conditioned the possibility of these last Middle Passages and the innovative forms of surveillance and communication deployed by those attempting to expose their practice runs as a constant theme throughout the study. For example, Harris illuminates the ways in which the unspeakable conditions of the Middle Passage transformed in relation to the modern technologies harnessed by the illegal traffickers. The promise of extraordinary profits and the risk of naval interception meant that ships were purchased for their advanced design, speed, and capacity. In the end, captives were enduring the Atlantic crossing under the power of steam. Limiting the amount of time spent on the African coast reduced the risk of capture and so, unlike previously, voyages were fully provisioned prior to their departure across the Atlantic. The cutting-edge slave ships required fewer crew than had been standard practice, in part, because the proportion of children forced aboard vessels expanded. Crucial information dispatched by traffickers and their antagonists circulated around the Atlantic by telegram.

The proximity of the Portuguese Company to the spies and officials, who either collected information or ignored their activities, lies at the core of this fascinating study. Sequestered in downtown Manhattan, Harris shows how these men had homes and offices just doors away from the British consulate and expedited their business under the noses of state officials. That the transatlantic slave trade was flourishing out of New York during the 1850s was not a secret only known by the authorities, however. It was extensively reported in the mainstream press and the subject of international debate. Harris's attention to the wider context in which New York could play such a pivotal role in this last murderous spurt of transatlantic slaving further illuminates the equivocal role played by United States in not only (largely failing to) suppress the international trafficking but actively enabling it to develop throughout the first half of the nineteenth century. One of the chief factors shaping the last decades of the slave trade, alongside powerful figures turning a blind eye, was the consistent refusal of the United States to sign any bilateral anti-slave trade treaty with Britain or to grant a British Right of Search. The federal insistence on maintaining sovereignty at sea meant that the United States flag became the international pennant of choice for illegal slave traders all around the Atlantic world. It was not until 1861 that the Right of Search was granted, and it was not until 1862 that Nathaniel Gordon became the first, and only, North American slave trader to be convicted and sentenced to death under the 1820 federal Anti-Slave Trade Act.

By the mid-1850s, the open question of the illegal slave trade had become enmeshed in national political debates concerning the extension of American slavery in the South, the possible re-opening of the transatlantic slave trade, and imperial ambition focused towards annexing Cuba. Harris deftly threads his analysis of the Democratic and Republican positions on these issues through the alarmist reports and rhetorically florid opinion pieces that flooded the national press to show how the contradictions of the slave-holding republic increasingly pressured the long-held assumption that domestic slavery and the transatlantic slave trade were somehow unrelated. While he alludes briefly to the abolitionist press in this context, Harris might have paid further attention to the role of local anti-slavery agitation from below, and particularly to the direct action and writings of radical African American abolitionists in these political debates. For example, during the 1830s and 1840s, African American abolitionists insisted on exposing New York as key to the ongoing transatlantic trade with their bodies and their words thereby helping to internationalise the African American anti-slavery struggle. The febrile political context of the 1850s fuelled Martin Delaney's revolutionary novel, Blake, in which captive rebels arrived from Africa to overturn Cuba and precipitate the destruction of slavery in the United States.

The Last Slave Ships is a landmark academic study that will no doubt inspire further research devoted to further exploring this long-neglected phase of the transatlantic slave trade. The skilfully developed transnational approach mobilised in the book is a model of historical scholarship. Placing New York at the heart of the wider nineteenth-century Atlantic world of illegal transatlantic slaving is also of public historical importance. This timely, lucid, and highly engaging book needs to find as wide an audience as possible.