Douglas County is located in the U.S. state of Kansas. Its county seat and most populous city is Lawrence. As of the 2020 census, the county population was 118,785, making it the fifth-most populous county in Kansas. The county was named after Stephen Douglas, a U.S. Senator from Illinois and advocate for the popular sovereignty choice in the Kansas slavery debate.

Bleeding Kansas, Bloody Kansas, or the Border War was a series of violent civil confrontations in Kansas Territory, and to a lesser extent in western Missouri, between 1854 and 1859. It emerged from a political and ideological debate over the legality of slavery in the proposed state of Kansas.