Jayhawkers is a term that came to prominence just before the American Civil War in Bleeding Kansas, where it was adopted by militant bands affiliated with the free-state cause. These bands, known as "Jayhawkers", were guerrilla fighters who often clashed with pro-slavery groups from Missouri known at the time as "Border Ruffians". After the Civil War, the word "Jayhawker" became synonymous with the people of Kansas. Today the term is used as a nickname for a native-born Kansan.