This question was put forth by the Republic of Texas in a referendum on December 29, 1845, to decide whether Texas should join the United States as a state. Voters overwhelmingly approved annexation by a margin of 4,134 votes to 407, and Texas was subsequently admitted to the Union as the 28th state on December 29, 1845.
The annexation was controversial at the time, as many in the United States feared that it would lead to war with Mexico, which also claimed the territory of Texas. Additionally, the issue of slavery played a role in the debate, as Texas allowed slavery while the United States was divided between free and slave states.
The Texas question ultimately contributed to the outbreak of the Mexican-American War in 1846, which resulted in the United States gaining control of the Southwest.