The ___extension_____ of slavery into new territories and states had been an issue as far back as the Northwest ___Ordinance____ of 1784. When the slave territory of Missouri sought statehood in 1818, Congress debated for two years before ___arriving____ upon the Missouri Compromise of 1820. This was the first of a series of political deals that resulted from ___arguments____ between pro-slavery and antislavery forces over the expansion of the “____peculiar___ institution,” as it was known, into the West.