Motives aside political calculus played a role in inspiring Southerners to stand against expansion. The commercial interests of the planter class did not necessarily line up with any kind of sectional political imperatives. Despite the fears of the radicals, vast tracks of Texas and Arkansas remained almost untouched. In time, more of Florida might see clearing. Alabama still had arable land not turned into plantations. Only in South Carolina had cotton cultivation probably reached its natural limits. The South still had internal frontiers to expand, to say nothing of any expansion into the Great Plains or the Caribbean Basin.
But set aside for a moment the land hunger: what if the filibusters won and brought in new slave states in the tropics? Tropical crops, and of course slaves, formed the backbone of the Southern economy. But the balmy American South would then face competition from the balmier still Caribbean basin. Taking Cuba could destroy Louisiana and Texas sugar profits, which already depended on a tariff that could not protect those states against a suddenly domestic product. Those planters might have to convert to cotton, which could drive prices down elsewhere. If the Caribbean ended up more focused on cotton, the same problem presented itself.
Cuba, annexed full of slaves, could crash the prices of slaves in the South and so wreck the Upper South’s lucrative export and the chief asset most planters, who often saw land more as an expense akin to seed than an asset in itself. The slaves cost more to acquire, after all. Even in the Lower South’s great economic boom, planters found themselves constrained less by available land than by available labor to work it. The Upper South could not supply enough slaves fast enough, which in turn played into racial fears about the future of whites in a South where it did.
That combination of economic need and racial fear gave impetus to the movement to reopen the African slave trade and to the dissenters from the same. But in the field of expansion, the fears also placed stronger limits on dreams for a Caribbean empire. Freehling’s The Road to Disunion: Seccessionists Triumphant has Calhoun expressing them:
John C. Calhoun a decade previously, when opposing the annexation of all of Mexico, had anticipated this foreboding about spreading slavery into polyglot areas, “More than half of the Mexicans are Indians,” he had winced, “and the other half is composed chiefly of mixed tribves. I protest against such a union as that!”
To that Freehling adds Calhoun’s fellow Carolinian, James Gadsden, of Gadsden Purchase fame:
You could not place a more irritating [cancer] on the Body Politic of our Federation than the annexation of Mexico-we have trouble enough with 3 millions of Africans.”
Worse still, what about all of Cuba’s free blacks? Or the Afro-Caribbean blacks who settled on the Nicaragua coast under British protection? Any free black could frighten a committed slavery booster, but thousands upon thousands? Would William Walker and his fellow filibusters have it in them to re-enslave those men and women in the name of white security? The racially hierarchical worldview that helped sustain slavery in the minds of the white South depended on status remaining static and exceptions to the rule that blacks labored and whites enjoyed the fruits of that labor kept to the margins where one could pretend they simply did not exist.
The racially mixed Caribbean, like beating heart of the expansionist movement in racially deviant New Orleans, could bring down that whole order. Nineteenth century America, North and South alike, belonged to whites. So many mixed-race people would invite both further racial amalgamation and admit the racially impure into the halls of power. White Charleston already couldn’t tell mixed-race people on sight and so demanded they wear veils. What would the balmy, sensual (many appeals to recruit filibusters mentioned women both beautiful and willing), Catholic, Latin, Creole, Indian, and Black Caribbean offer? Whites forced to share power and not even confident that everyone who appeared white actually had the proper racial credentials for admission to proper society.
With a far different outlook on race, we can neglect those concerns as irrelevant or marginal but to many nineteenth century Americans they struck to the very heart of their identities, to say nothing of their personal safety.