"the question respecting slavery in the old thirteen states had been decided and settled before the adoption of the constitution, which grants no power to congress to interfere with, or to change what had been so previously settled- the slave states therefore are free to continue or abolish slavery. since the year 1808 congress has possessed the power to prohibit and have prohibited the further immigration or importation of slaves into any of the old thirteen states, and at all times under the constitution have had power to prohibit such migration or importation into any of the new states, or territories of the united states… congress may therefore make it a condition of the admission of a new state that slavery shall be forever prohibited in the same. we may, with the more confidence, pronounce this to be the true construction of the constitution, as it has been so amply confirmed by the past congress."
-- united states senator rufus king, 1819
this excerpt from senator rufus king most directly reflects which goal for america's western territories?