Editing Compromise of 1850 (section)

==Background==
{{Further|Presidency of James K. Polk}}The [[Republic of Texas]] declared its independence from [[Mexico]] following the [[Texas Revolution]] of 1836, and, partly because Texas had been settled by a large number of Americans, there was a strong sentiment in both Texas and the United States for the annexation of Texas by the United States.<ref name=Merry120124>Merry, pp. 120–124</ref> In December 1845, President [[James K. Polk]] signed a resolution annexing Texas, and Texas became the 28th state in the union.<ref>Merry, pp. 211–212</ref> Polk, an expansionist and slave owner, sought further expansion through the acquisition of the Mexican province of [[Alta California]], which represented new lands to settle as well as a potential gateway to trade in [[Asia]].<ref>Howe, pp. 735–736</ref> His administration attempted to purchase California from Mexico,<ref>Howe, p. 734</ref> but the annexation of Texas stoked tensions between Mexico and the United States.<ref>Merry, pp. 176–177</ref> Relations between the two countries were further complicated by Texas's claim to all land north of the Rio Grande; Mexico argued that the more northern [[Nueces River]] was the proper Texan border.<ref name=Merry187>Merry, p. 187</ref>

In March 1846, a [[Thornton Affair|skirmish]] broke out on the northern side of the Rio Grande, ending in the death or capture of dozens of American soldiers.<ref>Merry, pp. 240–242</ref> Shortly thereafter, the United States declared war on Mexico, beginning the [[Mexican–American War]].<ref name=merry246247>Merry, pp. 246–247</ref> In August 1846, Polk asked Congress for an appropriation that he hoped to use as a down payment for the purchase of California in a treaty with Mexico, igniting a debate over the status of future territories.<ref name=merry283285>Merry, pp. 283–285</ref> A freshman Democratic Representative, [[David Wilmot (politician)|David Wilmot]] of Pennsylvania, offered an amendment known as the [[Wilmot Proviso]] that would ban slavery in any newly acquired lands.<ref name=merry286289>Merry, pp. 286–289</ref> The Wilmot Proviso was defeated in the Senate, but it injected the slavery debate into national politics.<ref>McPherson, pp. 53–54</ref>

In September 1847, an American army under General [[Winfield Scott]] captured the Mexican capital in the [[Battle for Mexico City]].<ref name=merry387388>Merry, pp. 387–388</ref> Several months later, Mexican and American negotiators agreed to the [[Treaty of Guadalupe Hidalgo]], under which Mexico agreed to recognize the Rio Grande as Texas's southern border and to cede Alta California and [[Santa Fe de Nuevo México|New Mexico]].<ref name=merry422426>Merry, pp. 424–425</ref> The [[Missouri Compromise]] had settled the issue of the geographic reach of slavery within the [[Louisiana Purchase]] territories by prohibiting slavery in states north of 36°30′ latitude, and Polk sought to extend this line into the newly acquired territory.<ref name=merry452453>Merry, pp. 452–453</ref> However, the divisive issue of slavery blocked any such legislation. As his term came to a close, Polk signed the lone territorial bill passed by Congress, which established the [[Oregon Territory|Territory of Oregon]] and banned slavery in it.<ref>Merry, pp. 460–461</ref> Polk declined to seek re-election in the [[1848 United States presidential election|1848 presidential election]],<ref name=merry376377>Merry, pp. 376–377</ref> and the 1848 election was won by the Whig ticket of [[Zachary Taylor]] and [[Millard Fillmore]].<ref name=merry447-448>Merry, pp. 447–448</ref>

Prophetically, [[Ralph Waldo Emerson]] quipped that "Mexico will poison us", referring to the ensuing divisions around whether the newly conquered lands would be slave or free.{{Sfn|McPherson|1988|p=51}} As of the 1848 election of Taylor, the issue was not yet apparent. Taylor was both a Whig and a slaveholder; though Whigs were increasingly anti-slavery, Taylor's slaveholding had reassured the South, and he won handily. Taylor made a key electoral promise that he would not veto any congressional resolution on slavery. Much to the horror of Southerners, however, Taylor indicated that true to his promise, he would not even veto the Wilmot Proviso if it were passed. Tensions accelerated quickly into the fall of 1849. Midterm elections worsened matters, as the [[Free Soil Party]] had gained 12 seats, which gave them a king-maker position in the closely divided House: 105 Whigs to 112 Democrats. After three weeks and 62 ballots, the House could not elect a speaker; the main issue was slavery in the new territories. The tumult of that period was severe, with a loaded revolver drawn on the floor of Congress, several fistfights between Northerners and Southerners, and then Senator [[Jefferson Davis]] challenging an Illinois representative to a duel. Southern representatives increasingly bandied around the idea of secession. Finally, the House adopted a resolution that allowed a speaker to be elected with a plurality, and elected [[Howell Cobb]] on the 63rd ballot. As [[James M. McPherson|James McPherson]] puts it: "It was an inauspicious start to the 1850's."{{Sfn|McPherson|1988|pp=64–68}}