Texas annexation admitted the Republic of Texas as the 28th U.S. state, expanding slave territory and triggering the Mexican–American War.
Key Facts
- Admission date
- December 29, 1845
- State number
- 28th state of the Union
- Texas independence declared
- March 2, 1836
- Annexation bill signed
- March 1, 1845, by President Tyler
- Senate treaty rejection
- June 1844, Whig majority voted against
- Formal union entry
- February 19, 1846
By the Numbers
Location
Cause → Event → Consequence
The Republic of Texas declared independence from Mexico in 1836 and immediately sought U.S. annexation, but political opposition over slavery and fear of war with Mexico blocked the bid for nearly a decade. By the early 1840s, declining Texan finances and British diplomatic interest in the region prompted President Tyler to pursue annexation secretly, and the 1844 election of pro-expansion Democrat James K. Polk provided the decisive political momentum.
Through a joint congressional resolution rather than a two-thirds Senate treaty ratification, President Tyler signed the annexation bill on March 1, 1845, and forwarded immediate annexation terms to Texas. Texans approved the agreement by popular vote, and President Polk signed the final bill on December 29, 1845, formally admitting Texas as the 28th state of the United States.
Texas formally joined the Union on February 19, 1846. Mexico, which had never recognized Texan independence, viewed annexation as an act of aggression. Border disputes along the Rio Grande led directly to the outbreak of the Mexican–American War in April 1846, ultimately resulting in vast territorial cessions to the United States and intensifying the national debate over the expansion of slavery.