U.S. Annexation of Texas: Date and Consequences

Date: December 29, 1845

Results of Annexation

• Texas became the 28th U.S. state.
• Annexation triggered the Mexican–American War (1846–1848).
• The war resulted in U.S. acquisition of vast southwestern territory (present‑day CA, NV, UT, AZ, NM).
• Texas entered as a slave state, intensifying sectional tensions over slavery that eventually led to the Civil War (1861–1865).