Texas Annexed as Slave State Despite Nine Years of Antislavery Opposition

Congress admits Texas to the Union as the 28th state on December 29, 1845, following a nine-year political struggle that delayed annexation due to opposition from antislavery forces. The annexation represents a clear victory for Slave Power expansion: Texas arrives as a vast slave-holding region (approximately 125,000 people with 30,000 enslaved) at a time when the political balance between free and slave states threatens to tear the nation apart. President John Tyler, unable to secure Senate ratification of an annexation treaty in June 1844, instead engineers annexation through a joint resolution of Congress requiring only simple majorities—a dubious constitutional workaround that bypasses the treaty process specifically to avoid the two-thirds Senate vote needed for ratification. The annexation violates Mexico’s sovereignty (Mexico had outlawed slavery and refused to recognize Texas independence), guarantees war with Mexico, and immediately triggers fierce sectional debates over slavery’s expansion into western territories that persist until the Civil War.

From the beginning, Texas becomes central to the growing sectional debate over slavery in America. Initially, Presidents Andrew Jackson and Martin Van Buren rejected annexing Texas specifically because slavery existed there and threatened national unity. In September 1836, Texas voted overwhelmingly for annexation, but when the Texas minister at Washington proposed annexation to the Van Buren administration in August 1837, he was told the proposition could not be entertained—constitutional scruples and fear of war with Mexico were cited, but antislavery sentiment was clearly the chief obstacle to annexation. Secretary of State John C. Calhoun engendered much northern opposition with his defense of annexation on grounds that it was necessary to protect slavery against British abolitionism. In June 1844, the Senate, with its Whig majority, soundly rejected the Tyler-Texas treaty.

Pro-annexation forces, in alliance with pro-expansion northern Democrats, secured the nomination of James K. Polk, who ran on a pro-Texas Manifest Destiny platform. After Polk narrowly defeated anti-annexation Whig Henry Clay in the 1844 presidential election, lame-duck President Tyler pushed through the joint resolution in February 1845. Abolitionists in the United States worried correctly that adding another slave-holding state would upset the political balance in Congress and in the country. The annexation proves to be a direct cause of the Mexican-American War (1846-1848) and solidifies the question of slavery’s expansion into western territories as the key issue driving the nation toward Civil War. The struggle over annexing Texas as a slave state makes many northerners willing to oppose slavery’s move into western territories (as framed in the Wilmot Proviso) or even consider supporting abolition. The annexation demonstrates institutional corruption through constitutional manipulation (joint resolution instead of treaty), the subordination of international law to slavery interests, and the willingness of political elites to risk war and national disunion to expand slavery’s economic base.