The first violent conflicts leading up to the Civil War occurred between two neighboring Midwestern states, Kansas and Missouri, involving anti-slavery Free-Staters and pro-slavery "Border Ruffian" elements, that took place in the Kansas Territory and the western frontier towns of Missouri roughly between 1854 and 1858. At the heart of the conflict was the question of whether Kansas would enter the Union as a free state or slave state. As such, Bleeding Kansas was a proxy war between Northerners and Southerners over the issue of slavery. The term "Bleeding Kansas" was coined by Horace Greeley of the "New-York Tribune"; the events it encompasses directly presaged the Civil War.