The conflict was fought politically, and between civilians, where it eventually degenerated into brutal gang violence and paramilitary guerrilla warfare.

Kansas was admitted to the Union as a free state the same day that enough Southern senators had departed, during the secession crisis that led to the Civil War, to allow it to pass (effective January 29, 1861).

As abolitionism became increasingly popular in the United States and tensions between its supporters and detractors grew, the U.S. Congress maintained a tenuous balance of political power between Northern and Southern representatives.

The act was proposed by Senator Stephen A. Douglas of Illinois as a way to appease Southern representatives in Congress, who had resisted earlier proposals to admit states from the Nebraska Territory because of the Missouri Compromise of 1820, which had explicitly forbidden the practice of slavery in all U.S. territory north of 36°30' latitude and west of the Mississippi River, except in the state of Missouri.

Southerners feared the incorporation of Nebraska would upset the balance between slave and free states and thereby give abolitionist Northerners an advantage in Congress.

Douglas's proposal attempted to allay these fears with the organization of two territories instead of one, and with the inclusion of a "popular sovereignty" clause that would, like the condition previously prescribed for Utah and New Mexico, permit settlers of Kansas and Nebraska to vote on the legality of slavery in their own territories—a notion which directly contradicted and effectively repealed the Missouri Compromise, as both Kansas and Nebraska were located entirely north of parallel 36°30' north and west of the Mississippi.

In Kansas, however, the assumption of legal slavery underestimated abolitionist resistance to the repeal of the long-standing Missouri Compromise.

Each side of the slavery question saw a chance to assert itself in Kansas, and it quickly became the nation's prevailing ideological battleground,[8] and the most violent place in the country.

Immediately, immigrants supporting both sides of the slavery question arrived in the Kansas Territory to establish residency and gain the right to vote.

Territorial Governor Andrew Reeder pleased neither side when he invalidated, as tainted by fraud, the results in only 11 of the 40 legislative races.

Charles L. Robinson, a Massachusetts native and agent of the New England Emigrant Aid Company, was elected territorial governor.

[18] The presence of dual governments was symptomatic of the strife brewing in the territory and further provoked supporters of both sides of the conflict.

[17][21] The report also stated that the legislature actually seated in Lecompton "was an illegally constituted body, and had no power to pass valid laws".

The proposed constitution was forwarded to the U.S. Senate on January 6, 1859, where it was met with a tepid reception and left to die in committee.

[24] The fourth and final Free State proposal was the Wyandotte Constitution, drafted in 1859, which represented the anti-slavery view of the future of Kansas.

Governor Wilson Shannon called for the Kansas militia, but the assembled army was composed almost entirely of proslavery Missourians, who camped outside the town of Lawrence with stolen weapons and a cannon.

In response, Lawrence raised its own militia, led by Charles L. Robinson, the man elected governor by the Topeka legislature, and James H. Lane.

The parties besieging Lawrence reluctantly dispersed only after Shannon negotiated a peace agreement between Robinson and Lane and David Rice Atchison.

[27][28][29] In May 1856, Republican Senator Charles Sumner of Massachusetts took to the floor to denounce the threat of slavery in Kansas and humiliate its supporters.

[31] Two days later, Butler's cousin, the South Carolina Congressman Preston Brooks, nearly killed Sumner on the Senate floor with a heavy cane.

In the coming weeks, many proslavery Democrats wore necklaces made from broken pieces of the cane as a symbol of solidarity with Preston Brooks.

John Brown led his sons and other followers to plan the murder of settlers who spoke in favor of slavery.

Brown and his men escaped and began plotting a full-scale slave insurrection to take place at Harpers Ferry, Virginia, with financial support from Boston abolitionists.

The last major outbreak of violence was touched off by the Marais des Cygnes massacre in 1858, in which Border Ruffians killed five Free State men.

In the so-called Battle of the Spurs, in January 1859, John Brown led escaped slaves through a proslavery ambush en route to freedom via Nebraska and Iowa; not a shot was fired.

[39] The congressional legislative deadlock was broken in early 1861, when following the election of Abraham Lincoln as President, seven Southern states seceded from the Union.

Without control of Missouri, regular Confederate forces were never in a position to seriously threaten the newly recognized free state government in Kansas.

In 2006, federal legislation defined a new Freedom's Frontier National Heritage Area (FFNHA) and was approved by Congress.

[40] The "Bleeding Kansas" period has been dramatically rendered in many works of American popular culture, including literature, theater, film, and television.