As tensions over slavery heated up in the 1850s, Congress decided to allow the citizens living in the Kansas territory to decide for themselves through the ballot whether or not the state would enter the union as a free or a slave state, a well-meant but ultimately disastrous attempt to defuse a volatile situation. This led both sides of the slavery debate, those who believed in freedom for all people and those who believed in slavery, to flood into the territory to try to influence the vote. Tensions escalated sharply, and violent incidents and clashes followed. Pro-slavers called "border ruffians" came over the border from Missouri, a slave state, and burned, looted, and killed in order to intimidate the abolitionists. John Brown, an abolitionist later famous for the Harper's Ferry raid, led a band of people in violence against the pro-slavers. Violence grew and erupted into a situation akin to a civil war. Though Kansas eventually came into the country as a free state in 1861, the events there helped legitimize the idea of violence as a solution to the slavery problem. The bloody events, and their use as propaganda by both sides also increased polarization and hatred, further hardening the uncompromising positions that led to the Civil War.