Adding the Lone Star: John Tyler, Sam Houston, and the Annexation of Texas - Hardcoverby Jordan T. Cash (Author) The annexation of Texas was one of the most momentous actions the United States government took in the antebellum period. Apart from adding what was the largest state in the Union at that time, it expedited further avenues for westward expansion, exacerbated tensions with Mexico resulting in the Mexican American War, and accelerated the sectional conflict over slavery. While the familiar concept of Manifest Destiny gives the