The significance of the Annulment of the Missouri Compromise lies in its role in escalating tensions leading to the American Civil War. The Compromise was intended to address conflicts between free and slave states. Its repeal in 1854 through the Kansas-Nebraska Act allowed territories to decide on slavery through popular sovereignty, reigniting sectional conflicts. This led to violent confrontations, known as "Bleeding Kansas," and solidified the divide between the North and South. The annulment highlighted the failures of compromise in addressing deeply entrenched societal divides.