One of the issues at play in the interactions between the United States and the Republic of Texas was the eventual annexation of Texas by the U.S. There were two main difficulties with the issue of Texas joining the United States at the time: first, incorporating Texas into the Union might provoke Mexico; and second, Texas wished to join as a slave state.

On August 23, 1843, Mexican Foreign Minister Bocanegra informed U.S. Envoy Extraordinary and Minister Plenipotentiary to Mexico, Waddy Thompson, that U.S. annexation of Texas would be grounds for war. On March 1, 1845, U.S. President John Tyler signed a congressional joint resolution favoring the annexation of Texas. On March 4, 1845, U.S. President James Knox Polk noted his approval of the “reunion” of the Republic of Texas with the United States in his inaugural address. In response, the Mexican Minister of Foreign Affairs informed U.S. Minister to Mexico, Wilson Shannon, on March 28, 1845, that Mexico was severing diplomatic relations with the United States. In December 1845 Texas was admitted to the union as the twenty-eighth state. In April 1846, Mexican troops attacked what they perceived to be invading U.S. forces that had occupied territory claimed by both Mexico and the United States, and on May 13, the U.S. Congress declared war against Mexico.

Slavery and Cotton.

Another issue raised by the debate over Texan annexation was that of slavery. Since the early nineteenth century, Texas was a producer of cotton. It was also dependent upon slave labor to produce its cotton. The question of whether or not the United States should annex Texas came at a time of increased tensions between the Northern and Southern states of the Union over the legality and morality of slavery; thus the possibility of admitting Texas as another slave state proved to be contentious.

Additionally, there was another issue raised by the Texas-cotton nexus: that of the market for raw cotton. One of the largest export markets for North American raw cotton in the mid-nineteenth century was to Great Britain. As long as Texas remained an independent state, it could give Southern U.S. cotton plantation owners competition in terms of setting prices – to force them to be more competitive.