Texas, annexation of

In US history, the adoption of Texas, an independent republic since 1836, as a state in the Union in 1845. The US annexation of Texas was one of the causes of the Mexican War.

Although Texans had voted for annexation as early as 1836, when Texas achieved its independence, no agreement was reached between the republic and the USA until 1845. One of the main obstacles to annexation was growing antislavery sentiment in the USA. However, many Americans began to favour annexation because the British, wishing to prevent further US westward expansion, opposed such a move. In 1845 US Congress passed a joint resolution for annexing Texas to the United States. Under its terms, Texas would keep its public lands and have the option of creating up to four other new states within its boundaries. Slavery would be prohibited north of the line drawn by the Missouri Compromise (1820) and would be left to the vote of the settlers south of the line. Texas became the 28th state in the Union on 29 December 1845, and its new state government formally took office on 19 February 1846.