Because the Kansas-Nebraska Act stated that the future status of slavery in the territories would be decided by popular vote, antislavery Northerners and proslavery Southerners competed to win the region for their own section. Since Nebraska was too far north to attract slaveowners, Kansas became the arena of sectional conflict. For six years, pro- and anti-slavery factions fought in Kansas as popular sovereignty degenerated into violence.
Even before the 1854 act passed, Eli Thayer (1819-1899), a Worcester, Massachusetts, businessman, organized the New England Emigrant Aid company to promote emigration of New Englanders to Kansas to "vote to make it free." Alarmed by rumors that the Emigrant Aid Society had raised $5 million to make Kansas a haven for runaway slaves, proslavery Missourians formed "Sons of the South" to "repel the wave of fanaticism which threatens to break upon our border."
In May 1855, Kansas held a territorial election. Although only 1500 men were registered to vote, 6000 ballots were cast, many by proslavery "border ruffians" from Missouri. As a result, a proslavery legislature was elected. This body passed laws stipulating that only proslavery men could hold public office or serve as jurors and imposed five years' imprisonment on anyone questioning the legality of slavery in Kansas.
Free soilers called the election a fraud and held their own convention which drew up a constitution prohibiting slavery in Kansas and barring free blacks from the territory. When Congress convened in January 1856, it was confronted by two rival governments in Kansas. President Franklin Pierce threw his support behind the proslavery legislature and asked Congress to admit Kansas as a slave state.
In a speech, Gerrit Smith discusses the New England Emigrant Aid Society and the efforts of free soilers to make Kansas a free territory.
I deeply regret that Mr. [Eli] Thayer...has not yet arrived. He is the President of the New England Emigrant Aid Society.... I have, since coming into this Hall, been permitted to read a communication...just received from Missouri. We learn from this communication, that they have actually begun to organize Emigrant Aid Societies in that State also. But how different are they from the New England Society! A Missouri Society offers a large bounty to those, who will become actual inhabitants of Kansas, provided expressly however that they are "proslavery." The New England Society, on the contrary, gives no bounty to any. It gives information and advice impartially to all, who wish to emigrate to Kansas, and it builds mills and hotels in Kansas for the equal accommodation of all, be they proslavery or antislavery. Surely it is with an ill grace, that they, who see nothing wrong in one of these Missouri Societies, should impute officiousness and unfairness to the New England Society.
But to my society. I will say nothing just now of the repeal of the Missouri Compromise, except to say, that the repeal was very perfidious and very wicked. And but little need be said on this occasion of the doctrine of "squatter sovereignty." That doctrine is absurd, because inasmuch as a Territory belongs to the whole people of the United States, they the whole people are bound to govern it. It is not competent for them to abdicate, and to leave to a handful what belongs to all....
The people of Kansas went to that surpassingly fertile and beautiful portion of the earth to find homes for themselves.--They then undertook to make a government for themselves. But a parcel of unmitigated and desperate scoundrels in Missouri...were determined, that the people of Kansas should not make a government for themselves. They, these scoundrels, would make it for them. Accordingly they marched into Kansas. I say marched--for, in many cases, they entered Kansas in a military conquering style, with drums beating and flags flying. They took possession of the ballot-boxes, and elected whom they would. Instead of a Kansas government, a Missouri or border ruffian government was set up in Kansas. That a government, brought into being in this way, should enact the most diabolical and infamous statues, is not to be wondered at. A specimen of these statutes is that, which makes it a penitentiary offence to express an opinion against the rightfulness of slaveholding. The border ruffians now insisted, that the people of Kansas should obey these statutes, and be loyally subject to the government, which had been forced upon them. The people of Kansas could but refuse. To have yielded would have been to prove themselves to be little less base than their oppressors. It was now, that these oppressors marched an army into Kansas to enforce subjection. But...their whiskey gave out--and with it their courage. Moreover, what they heard of a new kind of rifle in the hands of the brave men of Kansas--a kind invented by one Sharp--produced a great quaking among them. At any rate, so it was, that they marched back again. All this time the Federal Administration--the powers at Washington--had done nothing, and said nothing, openly. Beyond doubt, however, they were all this time countenancing and encouraging the outrages, of which we have spoken. And now when the terror-stricken border ruffians had fallen back, the Administration came forward with its messages, and proclamations, and threats. I will not say, that it came forward to embolden the ruffians to a fresh invasion; nor to take their place: but I will say, that it came forward to do their work--the work of compelling submission to this foreign and ruffian people to govern themselves--even the handful that might be scattered over a broad National territory. In their eyes the chief glory of the Nebraska Bill was this doctrine. But now this slavery-serving Administration trampled this doctrine under foot, and utterly repudiated in practice what it had so ardently clung to in theory. For now it demanded in the name of all the military power of the nation, that the people of Kansas should submit to a government, not chosen by themselves, but forced upon them by others....
Such then is the unhappy condition to which the people of Kansas are reduced--such the wrongs, which they are suffering at the hands of the Federal Administration and the Missouri ruffians. And the sole terms on which these combined powers will consent to let the people of Kansas remain in Kansas--nay, will consent to let them live--is that they shall acknowledge this impudent and abominable despotism, which has been set up on their soil, and that they shall pollute their souls by perjury, and debase and extinguish their manhood by submitting to whatever their oppressors may lay upon them....