What year did the annexation of Texas occur?

The annexation of Texas occurred in 1845, making it a significant event in U.S. history. This event followed the Texas Revolution, in which Texas gained independence from Mexico in 1836. The desire to annex Texas was fueled by a belief in Manifest Destiny, the idea that the United States was destined to expand across the North American continent. The annexation was a contentious issue, as it raised concerns about the extension of slavery into new territories and contributed to the tensions leading up to the Mexican-American War, which began in 1846.

Understanding this context helps clarify why 1845 is the correct answer, as it marks the official admission of Texas as a state in the Union after years of political negotiation and public debate.