Signed by James Monroe in 1820, the Missouri Compromise preserved the Senate's slave-free balance and prohibited slavery in the Louisiana Purchase territory north of latitude 36°30′ (with the exception of Missouri itself). It bought roughly thirty years of relative sectional peace. The Compromise was effectively repealed by the Kansas–Nebraska Act of 1854 and then declared unconstitutional in Dred Scott v. Sandford (1857), which held that Congress lacked the power to prohibit slavery in the territories. Both events accelerated the slide to Civil War.