U.S. Senator
Mexican–American War and aftermath (1846–1853) In February 1846, the Texas legislature elected Houston and Thomas Jefferson Rusk as Texas's two inaugural U.S. senators. Houston chose to align with the Democratic Party, which contained many of his old political allies, including President Polk. As a former president of Texas, Houston is the only former foreign head of state to have served in the U.S. Congress. He was the first person to serve as the governor of a state and then be elected to the U.S. Senate by another state. In 2018,
Mitt Romney became the second.
William W. Bibb accomplished the same feat in reverse order. Breaking with the Senate tradition that held that freshman senators were not to address the Senate, Houston strongly advocated in early 1846 for the annexation of
Oregon Country. In the
Oregon Treaty, reached later in 1846, Britain and the United States agreed to split Oregon Country. Meanwhile, Polk ordered General
Zachary Taylor to lead a U.S. army to the
Rio Grande, which had been set as the Texas-Mexico border under the Treaty of Velasco; Mexico claimed the Nueces River constituted the true border. After a skirmish between Taylor's unit and the Mexican army, the
Mexican–American War broke out in April 1846. Houston initially supported Polk's prosecution of the war, but differences between the two men emerged in 1847. After two years of fighting, the United States defeated Mexico and, through the
Treaty of Guadalupe Hidalgo, acquired the
Mexican Cession. Mexico also agreed to recognize the Rio Grande as the border between Mexico and Texas. After the war, disputes over the extension of slavery into the
territories raised sectional tensions. Unlike most of his Southern colleagues, Houston voted for the
Oregon Bill of 1848, which organized
Oregon Territory as a free territory. Defending his vote to create a territory that excluded slavery, Houston stated "I would be the last man to wish to do anything injurious to the South, but I do not think that on all occasions we are justified in agitating [slavery]." He criticized both Northern
abolitionists and Democratic followers of Calhoun as extremists who sought to undermine the union. He supported the
Compromise of 1850, a sectional compromise on slavery on the territories. Under the compromise, California was admitted as a free state, the slave trade was prohibited in the District of Columbia, a more stringent
fugitive slave law was passed, and
Utah Territory and
New Mexico Territory were established. Texas gave up some of its claims on New Mexico, but it retained El Paso, Texas, and the United States assumed Texas's large public debt. Houston sought the Democratic nomination in the
1852 presidential election, but he was unable to consolidate support outside of his home state. The
1852 Democratic National Convention ultimately nominated
Franklin Pierce, a compromise nominee, who went on to win the election.
Pierce and Buchanan administrations (1853–1859) In 1854, Senator
Stephen A. Douglas led the passage of the
Kansas–Nebraska Act, which organized
Kansas Territory and
Nebraska Territory. The act also repealed the
Missouri Compromise, an act that had banned slavery in territories north of parallel 36°30′ north. Houston voted against the act, in part because he believed that Native Americans would lose much of their land as a result of the act. He also perceived that it would lead to increased sectional tensions over slavery. Houston's opposition to the Kansas–Nebraska Act led to his departure from the Democratic Party. In 1855, Houston began to be associated publicly with the American Party, the political wing of the
nativist and unionist
Know Nothing movement. The Whig Party had collapsed after the passage of the Kansas–Nebraska Act, and the Know Nothings and the anti-slavery
Republican Party had both emerged as major political movements. Houston's affiliation with the party stemmed in part from his fear of the growing influence of Catholic voters; though he opposed barring Catholics from holding office, he wanted to extend the
naturalization period for immigrants to 21 years. He was attracted to the Know Nothing's support for a Native American state as well the party's unionist stance. Houston sought the presidential nomination at the
Know Nothing party's 1856 national convention, but the party nominated former President
Millard Fillmore. Houston was disappointed by Fillmore's selection as well as the party platform, which did not rebuke the Kansas–Nebraska Act, but he eventually decided to support Fillmore's candidacy. Despite Houston's renewed support, the American Party split over slavery, and Democrat
James Buchanan won the
1856 presidential election. The American Party collapsed after the election, and Houston did not affiliate with a national political party for the remainder of his tenure in the senate. In the
1857 Texas gubernatorial election, Texas Democrats nominated
Hardin Richard Runnels, who supported the Kansas–Nebraska Act and attacked Houston's record. In response, Houston announced his own candidacy for governor, but Runnels defeated him by a decisive margin. It was the only electoral defeat of his career. After the gubernatorial election, the Texas legislature denied Houston re-election in the senate; Houston rejected calls to resign immediately and served until the end of his term in early 1859. ==Governor of Texas==