It has been said that the motive for the conquests from Mexico was the desire for slave territory. The attractive part of the new dominion was of course California. Arizona and New Mexico are arid regions, and the mineral wealth of Nevada was unknown. The peacefully acquired region of Oregon, far north, need not concern us, but Oregon became a free State in 1859. Early in the war a struggle began between Northerners and Southerners (to a large extent independent of party) in the Senate and the House as to whether slavery should be allowed in the conquered land or not. David Wilmot, a Northern Democratic Congressman, proposed a proviso to the very first money grant connected with the war, that slavery should be forbidden in any territory to be annexed. The "Wilmot Proviso" was proposed again on every possible occasion; Lincoln, by the way, sturdily supported it while in Congress; it was always voted down. Cass proposed as a solution of all difficulties that the question of slavery should be left to the people of the new Territories or States themselves. The American public, apt as condensing an argument into a phrase, dismissed Cass's principle for the time being with the epithet "squatter sovereignty." Calhoun and his friends said it was contrary to the Constitution that an American citizen should not be free to move with his property, including his slaves, into territory won by the Union. The annexation was carried out, and the question of slavery was unsettled. Then events took a surprising turn. In the winter of 1848 gold was discovered in California. Throughout 1849 gold-seekers came pouring in from every part of the world. This miscellaneous new people, whose rough ways have been more celebrated in literature than those of any similar crowd, lived at first in considerable anarchy, but they determined without delay to set up some regular system of government. In the course of 1849 they elected a Convention to draw up a State Constitution, and to the astonishment of all the States the Convention unanimously made the prohibition of slavery part of that Constitution. There was no likelihood that, with a further influx of settlers of the same sort, this decision of California would alter. Was California to be admitted as a State with this Constitution of its own choice, which the bulk of the people of America approved?