While the Emigrant Aid Societies fit comfortably into the history of American settlement, that did not stop the people of western Missouri from seeing them as interlopers. Didn’t those New Englanders have their own territory just up north in Nebraska? Good Missouri men and women had waited for years at the frontier, some more observant of the law against moving across the line into Kansas than others, and now insulting outsiders would flood in and take it all from them. If the people coming under the auspices of the Massachusetts, later New England, Emigrant Aid Society and others had every right to the territory, a proposition many in Missouri would contest, then so did they.
This all must sound a bit remote from slavery. Whatever promises to the contrary, few slaveholders would risk their valuable human property on land that they would share with avowed abolitionists. The slaves might get ideas about freedom and find whites to help them escape. Worse still, they might find themselves inspired to violent revolution. Most of the Missourians who came to Kansas to stay probably cared far more about getting their land than the fate of slavery.
Interest in the fate of Kansas, however, extended well beyond the small Missouri farmer. The slaveholders of the Missouri valley lived too close and had too much invested to leave the matter to chance. They, like their smallholding neighbors, lived quite near to Kansas. With the governor not arriving until the fall, they also had and ample opportunity to arrange things across the border to their liking.
They did not waste the chance. In Westport, a group formed calling itself the Platte County Self-Defense Association. Its founders included David Rice Atchison and his trusted lieutenant Benjamin Franklin Stringfellow. They swore themselves to taking Kansas for slavery. To that end, they would take slaves into Kansas, keep them, and run out any abolitionist or free black they came upon. In Independence, proslavery men set up a vigilance (read: vigilante) committee and committees of correspondence throughout Kansas and the South to monitor events and promote settlement by reliable, proslavery men. Unlike those moving to Kansas permanently, these groups cared more about the slavery than the land. More precisely, they cared about their slavery on their land in Missouri and saw a free Kansas as threatening it.
On June 10, people inside Kansas got into the act with a meeting at Fort Leavenworth promising no protection to any abolitionist. Why would these people, presumably in Kansas on their own behalf and thus more interested in the land than slavery, make such a declaration?
Abolitionists settling in Kansas might encourage free blacks to do the same. This might further lead to communities of runaways who would settle down next door and become still more competition. In all that, they probably thought much better of most of the antislavery men coming to Kansas than the latter deserved. With few exceptions, most of the white antislavery movement shared with proslavery whites the vision of a future lily-white America. Such visions animated laws in Indiana and Illinois to exclude all blacks from those states only a few years before. No less an antislavery man than David Wilmot infamously declared that
I have no squeamish sensitiveness upon the subject of slavery, no morbid sympathy for the slave. I plead the cause and rights of white freemen. I would preserve to free white labor a fair country, a rich inheritance, where the sons of toil, of my own race and own color, can live without the disgrace which association with negro slavery brings upon free labor.
In addition to that, to live in Missouri, especially the western part, at least implied a level of comfort with slavery and facilitated a kind of shared racial solidarity with slaveholders. They might not precisely share the same class, but a poor farmer who had little could take some pride in being treated well by a rich man on the grounds of their shared color. They could have had business dealings with their slaveholding neighbors. They could very well share the slaveholders’ nightmares about servile insurrections. Would enraged, rebelling slaves really confine themselves only to the whites who personally owned them? If all those slaves turned free, could poorer whites really compete with the suddenly free labor? Would not social equality soon follow?
And if none of that convinced the Missouri smallholder moving into Kansas, then slaveholding neighbors remained neighbors. One could not say the same for Yankee interlopers. If their neighbors cared more about slavery than land, but would help secure the land in the name of securing slavery, then why would a Missourian emigrant object to joining forces?