... secured by the Ordinance of 1787. In 1807, Congress passed an act for the abolition of the slave-trade on Jan. 1, 1808. Slavery in part of the Louisiana Purchase, including the present States of Iowa , Oregon, Kansas, Nebraska, part of Colorado, and part of Minnesota, was abolished by the Missouri compromise (q. v..), whose validity was rejected by the Supreme Court (see Dred Scott decision); but ...