What year did Texas join the United States?

Texas joined the United States in 1845, making this the correct answer. After gaining independence from Mexico in 1836, Texas operated as an independent republic for nearly a decade. The decision to join the United States was influenced by various factors, including economic issues, threats from Mexico, and the desire for greater security and stability. The annexation was formalized when Congress passed a joint resolution to admit Texas as the 28th state on December 29, 1845.

The other years listed signify important events in Texas history but are not related to its statehood. For example, 1836 marks the year Texas declared independence from Mexico, while 1850 relates to the Compromise of 1850, which addressed several issues arising from Texas' statehood. Finally, 1861 is significant as it marks Texas' secession from the Union during the Civil War.