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The slavery extension question had seemingly been settled by the Missouri Compromise nearly 40 years earlier. The Mexican War, however, had added new territories, and the issue flared up again in the 1840s. The Compromise of 1850 provided a temporary respite from sectional strife, but the Kansas-Nebraska Act of 1854—a measure Douglas sponsored—brought the slavery extension issue to the fore once again. Douglas’s bill in effect repealed the Missouri Compromise by lifting the ban against slavery in territories north of the 36°30′ latitude. In place of the ban, Douglas offered popular sovereignty, the doctrine that the actual settlers in the territories and not Congress should decide the fate of slavery in their midst.