[211]
In December 1848, Polk sought to establish territorial governments in California and New Mexico, a task made especially urgent by the onset of the California Gold Rush.[212] The divisive issue of slavery blocked the idea. Finally in the Compromise of 1850 the issue was resolved.[213]
Polk had misgivings about a bill creating the Department of the Interior (March 3, 1849). He feared the federal government usurping power over public lands from the states. Nevertheless he signed the bill.[214]

Other initiatives[edit]
Polk's ambassador to the Republic of New Granada, Benjamin Alden Bidlack, negotiated the Mallarino–Bidlack Treaty.[215] Though Washington had initially only sought to remove tariffs on American goods, Bidlack and New Granadan Foreign Minister negotiated a broad agreement that deepened military and trade ties. The U.S. guaranteed New Granada's sovereignty over the Isthmus of Panama.[215] The treaty was ratified in 1848 and in the long run it facilitated the Panama Canal, built in the early 20th century.[216]  It allowed for the construction of the Panama Railway, which opened in 1855. The railway, built and operated by Americans and protected by the U.S. military, gave a quicker, safer journey to California and Oregon.  