[206]

Postwar and the territories[edit]
United States states and territories when Polk entered office
United States states and territories when Polk left office
Polk was anxious to establish a territorial government for Oregon but the matter became embroiled in the arguments over slavery, though few thought Oregon suitable for that institution. Bills to establish a territorial government passed the House twice but died in the Senate. By the time Congress met again in December, California and New Mexico were in U.S. hands, and Polk in his annual message urged the establishment of territorial governments in all three.[207] The Missouri Compromise had settled the issue of the geographic reach of slavery within the Louisiana Purchase by prohibiting slavery in states north of 36°30′ latitude, and Polk sought to extend this line into the newly acquired territory.[208] This would have made slavery illegal in Oregon and San Francisco but allowed it in Los Angeles.[209] Such an extension of slavery was defeated in the House by a bipartisan alliance of Northerners.[210] In 1848 Polk signed a bill to establish the Territory of Oregon and prohibit slavery in it.