In what year did Texas join the United States?

Texas joined the United States in 1845. This event followed a period of independent existence as the Republic of Texas, which had declared its independence from Mexico in 1836. The annexation of Texas was a significant development in American history, as it not only expanded the territory of the United States but also heightened tensions over issues such as slavery and territorial expansion, which eventually contributed to the outbreak of the Civil War. The desire to annex Texas stemmed from both strategic and economic interests, as it was seen as a way to promote further westward expansion. The formal admission took place on December 29, 1845, making Texas the 28th state of the Union.

The other years mentioned are associated with different significant events in Texas history but do not pertain to its statehood. For example, 1861 marks the year Texas seceded from the Union to join the Confederacy, 1876 is the year Texas adopted its current state constitution, and 1901 is notable for the discovery of oil at Spindletop, which transformed the state's economy but is not related to its admission into the Union.