The Siege of Lawrence occurred on May 21, 1856, when pro-slavery activists attacked and ransacked the town of Lawrence, Kansas, which had been founded by anti-slavery settlers to help ensure that Kansas would become a "free state".
 The incident made worse the guerrilla war in Kansas Territory that became known as Bleeding Kansas.
Free-Staters were those settlers in Kansas Territory during the Bleeding Kansas era in the 1850s who opposed the extension of slavery to Kansas.
 The name derives from the term "free state", that is, a U.S. state without slavery.
The Pottawatomie massacre occurred during the night of May 24 and the morning of May 25, 1856.
 In reaction to the sacking of Lawrence, Kansas by pro-slavery forces, John Brown and a band of abolitionist settlers—some of them members of the Pottawatomie Rifles—killed five settlers north of Pottawatomie Creek in Franklin County, Kansas.
 This was one of the many bloody episodes in Kansas preceding the American Civil War, which came to be known collectively as Bleeding Kansas.
 Bleeding Kansas was largely brought about by the Missouri Compromise and the Kansas–Nebraska Act.
The New England Emigrant Aid Company (originally the Massachusetts Emigrant Aid Company) was a transportation company in Boston, Massachusetts, created to transport immigrants to the Kansas Territory to shift the balance of power so that Kansas would enter the United States as a free state, rather than a slave state.
 Created by Eli Thayer in the wake of the Kansas-Nebraska Act, which allowed the population of Kansas Territory to choose whether slavery would be legal, the Company is noted less for its direct impact than for the psychological impact it had on proslavery and antislavery elements.
 Thayer's prediction that the Company would eventually be able to send 20,000 immigrants a year never came to fruition, but it spurred Border Ruffians from nearby Missouri, where slavery was legal, to move to Kansas to ensure its admission to the Union as a slave state.
 That, in turn, further galvanized Free-Staters and enemies of Slave Power.
John Brown (May 9, 1800 – December 2, 1859) was an American abolitionist who believed and advocated that armed insurrection was the only way to overthrow the institution of slavery in the United States.
 Brown first gained attention when he led small groups of volunteers during the Bleeding Kansas crisis of 1856.
 Dissatisfied with the pacifism of the organized abolitionist movement, he said, "These men are all talk.
 What we need is action—action!"
 During the Kansas campaign, Brown commanded forces at the Battle of Black Jack and the Battle of Osawatomie.
 He and his supporters killed five supporters of slavery in the Pottawatomie massacre of May 1856 in response to the sacking of Lawrence by pro-slavery forces.
Martin Franklin Conway (November 19, 1827 – February 15, 1882) was a U.S. congressman, consul to France, abolitionist, and advocate of the Free-State movement in Kansas.
The Kansas–Nebraska Act of 1854 (10 Stat.
 277 ) created the territories of Kansas and Nebraska and was drafted by Democratic Senator Stephen A. Douglas of Illinois and President Franklin Pierce.
 The initial purpose of the Kansas–Nebraska Act was to open up thousands of new farms and make feasible a Midwestern Transcontinental Railroad.
 The popular sovereignty clause of the law led pro- and anti-slavery elements to flood into Kansas with the goal of voting slavery up or down, resulting in Bleeding Kansas.
The Marais des Cygnes massacre ( , , or ) is considered the last significant act of violence in Bleeding Kansas prior to the outbreak of the American Civil War.
 On May 19, 1858, approximately 30 men led by Charles Hamilton, a Georgian native and proslavery leader, crossed into the Kansas Territory from Missouri.
 They arrived at Trading Post, Kansas, in the morning and then headed back to Missouri.
 Along the way they captured 11 Free-Staters, none of whom were armed and, it is said, none of whom had participated in the ongoing violence.
 Most of the men knew Hamilton and apparently did not realize he meant them harm.
 These prisoners were led into a defile, where Hamilton ordered the men to shoot.
 He even shot and fired the first bullet himself.
 Five men were killed.
The present Constitution of the State of Kansas was originally known as the Wyandotte Constitution to distinguish it from earlier proposed state constitutions.
 Drawn up at Wyandotte (now part of Kansas City) in July 1859, it was the fourth constitution voted on by the people of Kansas Territory, as the battle between proslavery and antislavery forces during the Bleeding Kansas era spread to the debate over the terms of the new state's charter.
The Wakarusa War was a skirmish that took place in Kansas Territory during November and December 1855 as part of the Bleeding Kansas violence.
 It centered on Lawrence, Kansas, and the Wakarusa River Valley.

Question: Martin Franklin Conway was a U.S. congressman, consul to France, abolitionist, and advocate of which movement in Kansas, the movement was by those settlers in Kansas Territory during the Bleeding Kansas era in the 1850s who opposed the extension of slavery to Kansas?
Answer: Free-Staters